jsonata.js

(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.jsonata = f()}})(function(){var define,module,exports;return (function(){function r(e,n,t){function o(i,f){if(!n[i]){if(!e[i]){var c="function"==typeof require&&require;if(!f&&c)return c(i,!0);if(u)return u(i,!0);var a=new Error("Cannot find module '"+i+"'");throw a.code="MODULE_NOT_FOUND",a}var p=n[i]={exports:{}};e[i][0].call(p.exports,function(r){var n=e[i][1][r];return o(n||r)},p,p.exports,r,e,n,t)}return n[i].exports}for(var u="function"==typeof require&&require,i=0;i<t.length;i++)o(t[i]);return o}return r})()({1:[function(require,module,exports){
'use strict';

var isMergeableObject = function isMergeableObject(value) {
	return isNonNullObject(value)
		&& !isSpecial(value)
};

function isNonNullObject(value) {
	return !!value && typeof value === 'object'
}

function isSpecial(value) {
	var stringValue = Object.prototype.toString.call(value);

	return stringValue === '[object RegExp]'
		|| stringValue === '[object Date]'
		|| isReactElement(value)
}

// see https://github.com/facebook/react/blob/b5ac963fb791d1298e7f396236383bc955f916c1/src/isomorphic/classic/element/ReactElement.js#L21-L25
var canUseSymbol = typeof Symbol === 'function' && Symbol.for;
var REACT_ELEMENT_TYPE = canUseSymbol ? Symbol.for('react.element') : 0xeac7;

function isReactElement(value) {
	return value.$$typeof === REACT_ELEMENT_TYPE
}

function emptyTarget(val) {
	return Array.isArray(val) ? [] : {}
}

function cloneUnlessOtherwiseSpecified(value, options) {
	return (options.clone !== false && options.isMergeableObject(value))
		? deepmerge(emptyTarget(value), value, options)
		: value
}

function defaultArrayMerge(target, source, options) {
	return target.concat(source).map(function(element) {
		return cloneUnlessOtherwiseSpecified(element, options)
	})
}

function getMergeFunction(key, options) {
	if (!options.customMerge) {
		return deepmerge
	}
	var customMerge = options.customMerge(key);
	return typeof customMerge === 'function' ? customMerge : deepmerge
}

function getEnumerableOwnPropertySymbols(target) {
	return Object.getOwnPropertySymbols
		? Object.getOwnPropertySymbols(target).filter(function(symbol) {
			return target.propertyIsEnumerable(symbol)
		})
		: []
}

function getKeys(target) {
	return Object.keys(target).concat(getEnumerableOwnPropertySymbols(target))
}

function propertyIsOnObject(object, property) {
	try {
		return property in object
	} catch(_) {
		return false
	}
}

// Protects from prototype poisoning and unexpected merging up the prototype chain.
function propertyIsUnsafe(target, key) {
	return propertyIsOnObject(target, key) // Properties are safe to merge if they don't exist in the target yet,
		&& !(Object.hasOwnProperty.call(target, key) // unsafe if they exist up the prototype chain,
			&& Object.propertyIsEnumerable.call(target, key)) // and also unsafe if they're nonenumerable.
}

function mergeObject(target, source, options) {
	var destination = {};
	if (options.isMergeableObject(target)) {
		getKeys(target).forEach(function(key) {
			destination[key] = cloneUnlessOtherwiseSpecified(target[key], options);
		});
	}
	getKeys(source).forEach(function(key) {
		if (propertyIsUnsafe(target, key)) {
			return
		}

		if (propertyIsOnObject(target, key) && options.isMergeableObject(source[key])) {
			destination[key] = getMergeFunction(key, options)(target[key], source[key], options);
		} else {
			destination[key] = cloneUnlessOtherwiseSpecified(source[key], options);
		}
	});
	return destination
}

function deepmerge(target, source, options) {
	options = options || {};
	options.arrayMerge = options.arrayMerge || defaultArrayMerge;
	options.isMergeableObject = options.isMergeableObject || isMergeableObject;
	// cloneUnlessOtherwiseSpecified is added to `options` so that custom arrayMerge()
	// implementations can use it. The caller may not replace it.
	options.cloneUnlessOtherwiseSpecified = cloneUnlessOtherwiseSpecified;

	var sourceIsArray = Array.isArray(source);
	var targetIsArray = Array.isArray(target);
	var sourceAndTargetTypesMatch = sourceIsArray === targetIsArray;

	if (!sourceAndTargetTypesMatch) {
		return cloneUnlessOtherwiseSpecified(source, options)
	} else if (sourceIsArray) {
		return options.arrayMerge(target, source, options)
	} else {
		return mergeObject(target, source, options)
	}
}

deepmerge.all = function deepmergeAll(array, options) {
	if (!Array.isArray(array)) {
		throw new Error('first argument should be an array')
	}

	return array.reduce(function(prev, next) {
		return deepmerge(prev, next, options)
	}, {})
};

var deepmerge_1 = deepmerge;

module.exports = deepmerge_1;

},{}],2:[function(require,module,exports){
/**
 * © Copyright IBM Corp. 2018 All Rights Reserved
 *   Project name: JSONata
 *   This project is licensed under the MIT License, see LICENSE
 */

const utils = require('./utils');

/**
 * DateTime formatting and parsing functions
 * Implements the xpath-functions format-date-time specification
 * @type {{formatInteger, formatDateTime, parseInteger, parseDateTime}}
 */
const dateTime = (function () {
    'use strict';

    const stringToArray = utils.stringToArray;

    const few = ['Zero', 'One', 'Two', 'Three', 'Four', 'Five', 'Six', 'Seven', 'Eight', 'Nine', 'Ten',
        'Eleven', 'Twelve', 'Thirteen', 'Fourteen', 'Fifteen', 'Sixteen', 'Seventeen', 'Eighteen', 'Nineteen'];
    const ordinals = ['Zeroth', 'First', 'Second', 'Third', 'Fourth', 'Fifth', 'Sixth', 'Seventh', 'Eighth', 'Ninth', 'Tenth',
        'Eleventh', 'Twelfth', 'Thirteenth', 'Fourteenth', 'Fifteenth', 'Sixteenth', 'Seventeenth', 'Eighteenth', 'Nineteenth'];
    const decades = ['Twenty', 'Thirty', 'Forty', 'Fifty', 'Sixty', 'Seventy', 'Eighty', 'Ninety', 'Hundred'];
    const magnitudes = ['Thousand', 'Million', 'Billion', 'Trillion'];

    /**
     * converts a number into english words
     * @param {string} value - the value to format
     * @param {boolean} ordinal - ordinal or cardinal form
     * @returns {string} - representation in words
     */
    function numberToWords(value, ordinal) {
        var lookup = function (num, prev, ord) {
            var words = '';
            if (num <= 19) {
                words = (prev ? ' and ' : '') + (ord ? ordinals[num] : few[num]);
            } else if (num < 100) {
                const tens = Math.floor(num / 10);
                const remainder = num % 10;
                words = (prev ? ' and ' : '') + decades[tens - 2];
                if (remainder > 0) {
                    words += '-' + lookup(remainder, false, ord);
                } else if (ord) {
                    words = words.substring(0, words.length - 1) + 'ieth';
                }
            } else if (num < 1000) {
                const hundreds = Math.floor(num / 100);
                const remainder = num % 100;
                words = (prev ? ', ' : '') + few[hundreds] + ' Hundred';
                if (remainder > 0) {
                    words += lookup(remainder, true, ord);
                } else if (ord) {
                    words += 'th';
                }
            } else {
                var mag = Math.floor(Math.log10(num) / 3);
                if (mag > magnitudes.length) {
                    mag = magnitudes.length; // the largest word
                }
                const factor = Math.pow(10, mag * 3);
                const mant = Math.floor(num / factor);
                const remainder = num - mant * factor;
                words = (prev ? ', ' : '') + lookup(mant, false, false) + ' ' + magnitudes[mag - 1];
                if (remainder > 0) {
                    words += lookup(remainder, true, ord);
                } else if (ord) {
                    words += 'th';
                }
            }
            return words;
        };

        var words = lookup(value, false, ordinal);
        return words;
    }

    const wordValues = {};
    few.forEach(function (word, index) {
        wordValues[word.toLowerCase()] = index;
    });
    ordinals.forEach(function (word, index) {
        wordValues[word.toLowerCase()] = index;
    });
    decades.forEach(function (word, index) {
        const lword = word.toLowerCase();
        wordValues[lword] = (index + 2) * 10;
        wordValues[lword.substring(0, word.length - 1) + 'ieth'] = wordValues[lword];
    });
    wordValues.hundredth = 100;
    magnitudes.forEach(function (word, index) {
        const lword = word.toLowerCase();
        const val = Math.pow(10, (index + 1) * 3);
        wordValues[lword] = val;
        wordValues[lword + 'th'] = val;
    });

    /**
     * Converts a number in english words to numeric value
     * @param {string} text - the number in words
     * @returns {number} - the numeric value
     */
    function wordsToNumber(text) {
        const parts = text.split(/,\s|\sand\s|[\s\\-]/);
        const values = parts.map(part => wordValues[part]);
        let segs = [0];
        values.forEach(value => {
            if (value < 100) {
                let top = segs.pop();
                if (top >= 1000) {
                    segs.push(top);
                    top = 0;
                }
                segs.push(top + value);
            } else {
                segs.push(segs.pop() * value);
            }
        });
        const result = segs.reduce((a, b) => a + b, 0);
        return result;
    }

    const romanNumerals = [
        [1000, 'm'],
        [900, 'cm'],
        [500, 'd'],
        [400, 'cd'],
        [100, 'c'],
        [90, 'xc'],
        [50, 'l'],
        [40, 'xl'],
        [10, 'x'],
        [9, 'ix'],
        [5, 'v'],
        [4, 'iv'],
        [1, 'i']
    ];

    const romanValues = {'M': 1000, 'D': 500, 'C': 100, 'L': 50, 'X': 10, 'V': 5, 'I': 1};

    /**
     * converts a number to roman numerals
     * @param {number} value - the number
     * @returns {string} - the number in roman numerals
     */
    function decimalToRoman(value) {
        for (var index = 0; index < romanNumerals.length; index++) {
            const numeral = romanNumerals[index];
            if (value >= numeral[0]) {
                return numeral[1] + decimalToRoman(value - numeral[0]);
            }
        }
        return '';
    }

    /**
     * converts roman numerals to a number
     * @param {string} roman - roman number
     * @returns {number} - the numeric value
     */
    function romanToDecimal(roman) {
        var decimal = 0;
        var max = 1;
        for (var i = roman.length - 1; i >= 0; i--) {
            const digit = roman[i];
            const value = romanValues[digit];
            if (value < max) {
                decimal -= value;
            } else {
                max = value;
                decimal += value;
            }
        }
        return decimal;
    }

    /**
     * converts a number to spreadsheet style letters
     * @param {number} value - the number
     * @param {string} aChar - the character representing the start of the sequence, e.g. 'A'
     * @returns {string} - the letters
     */
    function decimalToLetters(value, aChar) {
        var letters = [];
        var aCode = aChar.charCodeAt(0);
        while (value > 0) {
            letters.unshift(String.fromCharCode((value - 1) % 26 + aCode));
            value = Math.floor((value - 1) / 26);
        }
        return letters.join('');
    }

    /**
     * converts spreadsheet style letters to a number
     * @param {string} letters - the letters
     * @param {string} aChar - the character representing the start of the sequence, e.g. 'A'
     * @returns {number} - the numeric value
     */
    function lettersToDecimal(letters, aChar) {
        var aCode = aChar.charCodeAt(0);
        var decimal = 0;
        for (var i = 0; i < letters.length; i++) {
            decimal += (letters.charCodeAt(letters.length - i - 1) - aCode + 1) * Math.pow(26, i);
        }
        return decimal;
    }

    /**
     * Formats an integer as specified by the XPath fn:format-integer function
     * See https://www.w3.org/TR/xpath-functions-31/#func-format-integer
     * @param {number} value - the number to be formatted
     * @param {string} picture - the picture string that specifies the format
     * @returns {string} - the formatted number
     */
    function formatInteger(value, picture) {
        if (typeof value === 'undefined') {
            return undefined;
        }

        value = Math.floor(value);

        const format = analyseIntegerPicture(picture);
        return _formatInteger(value, format);
    }

    const formats = {
        DECIMAL: 'decimal',
        LETTERS: 'letters',
        ROMAN: 'roman',
        WORDS: 'words',
        SEQUENCE: 'sequence'
    };

    const tcase = {
        UPPER: 'upper',
        LOWER: 'lower',
        TITLE: 'title'
    };

    /**
     * formats an integer using a preprocessed representation of the picture string
     * @param {number} value - the number to be formatted
     * @param {object} format - the preprocessed representation of the pucture string
     * @returns {string} - the formatted number
     * @private
     */
    function _formatInteger(value, format) {
        let formattedInteger;
        const negative = value < 0;
        value = Math.abs(value);
        switch (format.primary) {
            case formats.LETTERS:
                formattedInteger = decimalToLetters(value, format.case === tcase.UPPER ? 'A' : 'a');
                break;
            case formats.ROMAN:
                formattedInteger = decimalToRoman(value);
                if (format.case === tcase.UPPER) {
                    formattedInteger = formattedInteger.toUpperCase();
                }
                break;
            case formats.WORDS:
                formattedInteger = numberToWords(value, format.ordinal);
                if (format.case === tcase.UPPER) {
                    formattedInteger = formattedInteger.toUpperCase();
                } else if (format.case === tcase.LOWER) {
                    formattedInteger = formattedInteger.toLowerCase();
                }
                break;
            case formats.DECIMAL:
                formattedInteger = '' + value;
                // TODO use functionPad
                var padLength = format.mandatoryDigits - formattedInteger.length;
                if (padLength > 0) {
                    var padding = (new Array(padLength + 1)).join('0');
                    formattedInteger = padding + formattedInteger;
                }
                if (format.zeroCode !== 0x30) {
                    formattedInteger = stringToArray(formattedInteger).map(code => {
                        return String.fromCodePoint(code.codePointAt(0) + format.zeroCode - 0x30);
                    }).join('');
                }
                // insert the grouping-separator-signs, if any
                if (format.regular) {
                    const n = Math.floor((formattedInteger.length - 1) / format.groupingSeparators.position);
                    for (let ii = n; ii > 0; ii--) {
                        const pos = formattedInteger.length - ii * format.groupingSeparators.position;
                        formattedInteger = formattedInteger.substr(0, pos) + format.groupingSeparators.character + formattedInteger.substr(pos);
                    }
                } else {
                    format.groupingSeparators.reverse().forEach(separator => {
                        const pos = formattedInteger.length - separator.position;
                        formattedInteger = formattedInteger.substr(0, pos) + separator.character + formattedInteger.substr(pos);
                    });
                }

                if (format.ordinal) {
                    var suffix123 = {'1': 'st', '2': 'nd', '3': 'rd'};
                    var lastDigit = formattedInteger[formattedInteger.length - 1];
                    var suffix = suffix123[lastDigit];
                    if (!suffix || (formattedInteger.length > 1 && formattedInteger[formattedInteger.length - 2] === '1')) {
                        suffix = 'th';
                    }
                    formattedInteger = formattedInteger + suffix;
                }
                break;
            case formats.SEQUENCE:
                throw {
                    code: 'D3130',
                    value: format.token
                };
        }
        if (negative) {
            formattedInteger = '-' + formattedInteger;
        }

        return formattedInteger;
    }

    //TODO what about decimal groups in the unicode supplementary planes (surrogate pairs) ???
    const decimalGroups = [0x30, 0x0660, 0x06F0, 0x07C0, 0x0966, 0x09E6, 0x0A66, 0x0AE6, 0x0B66, 0x0BE6, 0x0C66, 0x0CE6, 0x0D66, 0x0DE6, 0x0E50, 0x0ED0, 0x0F20, 0x1040, 0x1090, 0x17E0, 0x1810, 0x1946, 0x19D0, 0x1A80, 0x1A90, 0x1B50, 0x1BB0, 0x1C40, 0x1C50, 0xA620, 0xA8D0, 0xA900, 0xA9D0, 0xA9F0, 0xAA50, 0xABF0, 0xFF10];

    /**
     * preprocesses the picture string
     * @param {string} picture - picture string
     * @returns {{type: string, primary: string, case: string, ordinal: boolean}} - analysed picture
     */
    function analyseIntegerPicture(picture) {
        const format = {
            type: 'integer',
            primary: formats.DECIMAL,
            case: tcase.LOWER,
            ordinal: false
        };

        let primaryFormat, formatModifier;
        const semicolon = picture.lastIndexOf(';');
        if (semicolon === -1) {
            primaryFormat = picture;
        } else {
            primaryFormat = picture.substring(0, semicolon);
            formatModifier = picture.substring(semicolon + 1);
            if (formatModifier[0] === 'o') {
                format.ordinal = true;
            }
        }

        /* eslnt-disable-next no-fallthrough */
        switch (primaryFormat) {
            case 'A':
                format.case = tcase.UPPER;
            /* eslnt-disable-next-line no-fallthrough */
            case 'a':
                format.primary = formats.LETTERS;
                break;
            case 'I':
                format.case = tcase.UPPER;
            /* eslnt-disable-next-line no-fallthrough */
            case 'i':
                format.primary = formats.ROMAN;
                break;
            case 'W':
                format.case = tcase.UPPER;
                format.primary = formats.WORDS;
                break;
            case 'Ww':
                format.case = tcase.TITLE;
                format.primary = formats.WORDS;
                break;
            case 'w':
                format.primary = formats.WORDS;
                break;
            default: {
                // this is a decimal-digit-pattern if it contains a decimal digit (from any unicode decimal digit group)
                let zeroCode = null;
                let mandatoryDigits = 0;
                let optionalDigits = 0;
                let groupingSeparators = [];
                let separatorPosition = 0;
                const formatCodepoints = stringToArray(primaryFormat).map(c => c.codePointAt(0)).reverse(); // reverse the array to determine positions of grouping-separator-signs
                formatCodepoints.forEach((codePoint) => {
                    // step though each char in the picture to determine the digit group
                    let digit = false;
                    for (let ii = 0; ii < decimalGroups.length; ii++) {
                        const group = decimalGroups[ii];
                        if (codePoint >= group && codePoint <= group + 9) {
                            // codepoint is part of this decimal group
                            digit = true;
                            mandatoryDigits++;
                            separatorPosition++;
                            if (zeroCode === null) {
                                zeroCode = group;
                            } else if (group !== zeroCode) {
                                // error! different decimal groups in the same pattern
                                throw {
                                    code: 'D3131'
                                };
                            }
                            break;
                        }
                    }
                    if (!digit) {
                        if (codePoint === 0x23) { // # - optional-digit-sign
                            separatorPosition++;
                            optionalDigits++;
                        } else {
                            // neither a decimal-digit-sign ot optional-digit-sign, assume it is a grouping-separator-sign
                            groupingSeparators.push({
                                position: separatorPosition,
                                character: String.fromCodePoint(codePoint)
                            });
                        }
                    }
                });
                if (mandatoryDigits > 0) {
                    format.primary = formats.DECIMAL;
                    // TODO validate decimal-digit-pattern

                    // the decimal digit family (codepoint offset)
                    format.zeroCode = zeroCode;
                    // the number of mandatory digits
                    format.mandatoryDigits = mandatoryDigits;
                    // the number of optional digits
                    format.optionalDigits = optionalDigits;
                    // grouping separator template
                    // are the grouping-separator-signs 'regular'?
                    const regularRepeat = function (separators) {
                        // are the grouping positions regular? i.e. same interval between each of them
                        // is there at least one separator?
                        if (separators.length === 0) {
                            return 0;
                        }
                        // are all the characters the same?
                        const sepChar = separators[0].character;
                        for (let ii = 1; ii < separators.length; ii++) {
                            if (separators[ii].character !== sepChar) {
                                return 0;
                            }
                        }
                        // are they equally spaced?
                        const indexes = separators.map(separator => separator.position);
                        const gcd = function (a, b) {
                            return b === 0 ? a : gcd(b, a % b);
                        };
                        // find the greatest common divisor of all the positions
                        const factor = indexes.reduce(gcd);
                        // is every position separated by this divisor? If so, it's regular
                        for (let index = 1; index <= indexes.length; index++) {
                            if (indexes.indexOf(index * factor) === -1) {
                                return 0;
                            }
                        }
                        return factor;
                    };

                    const regular = regularRepeat(groupingSeparators);
                    if (regular > 0) {
                        format.regular = true;
                        format.groupingSeparators = {
                            position: regular,
                            character: groupingSeparators[0].character
                        };
                    } else {
                        format.regular = false;
                        format.groupingSeparators = groupingSeparators;
                    }

                } else {
                    // this is a 'numbering sequence' which the spec says is implementation-defined
                    // this implementation doesn't support any numbering sequences at the moment.
                    format.primary = formats.SEQUENCE;
                    format.token = primaryFormat;
                }
            }
        }

        return format;
    }

    const defaultPresentationModifiers = {
        Y: '1', M: '1', D: '1', d: '1', F: 'n', W: '1', w: '1', X: '1', x: '1', H: '1', h: '1',
        P: 'n', m: '01', s: '01', f: '1', Z: '01:01', z: '01:01', C: 'n', E: 'n'
    };

    // §9.8.4.1 the format specifier is an array of string literals and variable markers
    /**
     * analyse the date-time picture string
     * @param {string} picture - picture string
     * @returns {{type: string, parts: Array}} - the analysed string
     */
    function analyseDateTimePicture(picture) {
        var spec = [];
        const format = {
            type: 'datetime',
            parts: spec
        };
        const addLiteral = function (start, end) {
            if (end > start) {
                let literal = picture.substring(start, end);
                // replace any doubled ]] with single ]
                // what if there are instances of single ']' ? - the spec doesn't say
                literal = literal.split(']]').join(']');
                spec.push({type: 'literal', value: literal});
            }
        };

        var start = 0, pos = 0;
        while (pos < picture.length) {
            if (picture.charAt(pos) === '[') {
                // check it's not a doubled [[
                if (picture.charAt(pos + 1) === '[') {
                    // literal [
                    addLiteral(start, pos);
                    spec.push({type: 'literal', value: '['});
                    pos += 2;
                    start = pos;
                    continue;
                }
                // start of variable marker
                // push the string literal (if there is one) onto the array
                addLiteral(start, pos);
                start = pos;
                // search forward to closing ]
                pos = picture.indexOf(']', start);
                // TODO handle error case if pos === -1
                if(pos === -1) {
                    // error - no closing bracket
                    throw {
                        code: 'D3135'
                    };
                }
                let marker = picture.substring(start + 1, pos);
                // whitespace within a variable marker is ignored (i.e. remove it)
                marker = marker.split(/\s+/).join('');
                var def = {
                    type: 'marker',
                    component: marker.charAt(0)  // 1. The component specifier is always present and is always a single letter.
                };
                var comma = marker.lastIndexOf(','); // 2. The width modifier may be recognized by the presence of a comma
                var presMod; // the presentation modifiers
                if (comma !== -1) {
                    // §9.8.4.2 The Width Modifier
                    const widthMod = marker.substring(comma + 1);
                    const dash = widthMod.indexOf('-');
                    let min, max;
                    const parseWidth = function (wm) {
                        if (typeof wm === 'undefined' || wm === '*') {
                            return undefined;
                        } else {
                            // TODO validate wm is an unsigned int
                            return parseInt(wm);
                        }
                    };
                    if (dash === -1) {
                        min = widthMod;
                    } else {
                        min = widthMod.substring(0, dash);
                        max = widthMod.substring(dash + 1);
                    }
                    const widthDef = {
                        min: parseWidth(min),
                        max: parseWidth(max)
                    };
                    def.width = widthDef;
                    presMod = marker.substring(1, comma);
                } else {
                    presMod = marker.substring(1);
                }
                if (presMod.length === 1) {
                    def.presentation1 = presMod; // first presentation modifier
                    //TODO validate the first presentation modifier - it's either N, n, Nn or it passes analyseIntegerPicture
                } else if (presMod.length > 1) {
                    var lastChar = presMod.charAt(presMod.length - 1);
                    if ('atco'.indexOf(lastChar) !== -1) {
                        def.presentation2 = lastChar;
                        if (lastChar === 'o') {
                            def.ordinal = true;
                        }
                        // 'c' means 'cardinal' and is the default (i.e. not 'ordinal')
                        // 'a' & 't' are ignored (not sure of their relevance to English numbering)
                        def.presentation1 = presMod.substring(0, presMod.length - 1);
                    } else {
                        def.presentation1 = presMod;
                        //TODO validate the first presentation modifier - it's either N, n, Nn or it passes analyseIntegerPicture,
                        // doesn't use ] as grouping separator, and if grouping separator is , then must have width modifier
                    }
                } else {
                    // no presentation modifier specified - apply the default;
                    def.presentation1 = defaultPresentationModifiers[def.component];
                }
                if (typeof def.presentation1 === 'undefined') {
                    // unknown component specifier
                    throw {
                        code: 'D3132',
                        value: def.component
                    };
                }
                if (def.presentation1[0] === 'n') {
                    def.names = tcase.LOWER;
                } else if (def.presentation1[0] === 'N') {
                    if (def.presentation1[1] === 'n') {
                        def.names = tcase.TITLE;
                    } else {
                        def.names = tcase.UPPER;
                    }
                } else if ('YMDdFWwXxHhmsf'.indexOf(def.component) !== -1) {
                    var integerPattern = def.presentation1;
                    if (def.presentation2) {
                        integerPattern += ';' + def.presentation2;
                    }
                    def.integerFormat = analyseIntegerPicture(integerPattern);
                    if (def.width && def.width.min !== undefined) {
                        if (def.integerFormat.mandatoryDigits < def.width.min) {
                            def.integerFormat.mandatoryDigits = def.width.min;
                        }
                    }
                    if (def.component === 'Y') {
                        // §9.8.4.4
                        def.n = -1;
                        if (def.width && def.width.max !== undefined) {
                            def.n = def.width.max;
                            def.integerFormat.mandatoryDigits = def.n;
                        } else {
                            var w = def.integerFormat.mandatoryDigits + def.integerFormat.optionalDigits;
                            if (w >= 2) {
                                def.n = w;
                            }
                        }
                    }
                }
                if (def.component === 'Z' || def.component === 'z') {
                    def.integerFormat = analyseIntegerPicture(def.presentation1);
                }
                spec.push(def);
                start = pos + 1;
            }
            pos++;
        }
        addLiteral(start, pos);
        return format;
    }

    const days = ['', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'];
    const months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];
    const millisInADay = 1000 * 60 * 60 * 24;

    const startOfFirstWeek = function (ym) {
        // ISO 8601 defines the first week of the year to be the week that contains the first Thursday
        // XPath F&O extends this same definition for the first week of a month
        // the week starts on a Monday - calculate the millis for the start of the first week
        // millis for given 1st Jan of that year (at 00:00 UTC)
        const jan1 = Date.UTC(ym.year, ym.month);
        var dayOfJan1 = (new Date(jan1)).getUTCDay();
        if (dayOfJan1 === 0) {
            dayOfJan1 = 7;
        }
        // if Jan 1 is Fri, Sat or Sun, then add the number of days (in millis) to jan1 to get the start of week 1
        return dayOfJan1 > 4 ? jan1 + (8 - dayOfJan1) * millisInADay : jan1 - (dayOfJan1 - 1) * millisInADay;
    };

    const yearMonth = function (year, month) {
        return {
            year: year,
            month: month,
            nextMonth: function () {
                return (month === 11) ? yearMonth(year + 1, 0) : yearMonth(year, month + 1);
            },
            previousMonth: function () {
                return (month === 0) ? yearMonth(year - 1, 11) : yearMonth(year, month - 1);
            },
            nextYear: function () {
                return yearMonth(year + 1, month);
            },
            previousYear: function () {
                return yearMonth(year - 1, month);
            }
        };
    };

    const deltaWeeks = function (start, end) {
        return (end - start) / (millisInADay * 7) + 1;
    };

    const getDateTimeFragment = (date, component) => {
        let componentValue;
        switch (component) {
            case 'Y': // year
                componentValue = date.getUTCFullYear();
                break;
            case 'M': // month in year
                componentValue = date.getUTCMonth() + 1;
                break;
            case 'D': // day in month
                componentValue = date.getUTCDate();
                break;
            case 'd': { // day in year
                // millis for given date (at 00:00 UTC)
                const today = Date.UTC(date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate());
                // millis for given 1st Jan of that year (at 00:00 UTC)
                const firstJan = Date.UTC(date.getUTCFullYear(), 0);
                componentValue = (today - firstJan) / millisInADay + 1;
                break;
            }
            case 'F': // day of week
                componentValue = date.getUTCDay();
                if (componentValue === 0) {
                    // ISO 8601 defines days 1-7: Mon-Sun
                    componentValue = 7;
                }
                break;
            case 'W': { // week in year
                const thisYear = yearMonth(date.getUTCFullYear(), 0);
                const startOfWeek1 = startOfFirstWeek(thisYear);
                const today = Date.UTC(thisYear.year, date.getUTCMonth(), date.getUTCDate());
                let week = deltaWeeks(startOfWeek1, today);
                if (week > 52) {
                    // might be first week of the following year
                    const startOfFollowingYear = startOfFirstWeek(thisYear.nextYear());
                    if (today >= startOfFollowingYear) {
                        week = 1;
                    }
                } else if (week < 1) {
                    // must be end of the previous year
                    const startOfPreviousYear = startOfFirstWeek(thisYear.previousYear());
                    week = deltaWeeks(startOfPreviousYear, today);
                }
                componentValue = Math.floor(week);
                break;
            }
            case 'w': { // week in month
                const thisMonth = yearMonth(date.getUTCFullYear(), date.getUTCMonth());
                const startOfWeek1 = startOfFirstWeek(thisMonth);
                const today = Date.UTC(thisMonth.year, thisMonth.month, date.getUTCDate());
                let week = deltaWeeks(startOfWeek1, today);
                if (week > 4) {
                    // might be first week of the following month
                    const startOfFollowingMonth = startOfFirstWeek(thisMonth.nextMonth());
                    if (today >= startOfFollowingMonth) {
                        week = 1;
                    }
                } else if (week < 1) {
                    // must be end of the previous month
                    const startOfPreviousMonth = startOfFirstWeek(thisMonth.previousMonth());
                    week = deltaWeeks(startOfPreviousMonth, today);
                }
                componentValue = Math.floor(week);
                break;
            }
            case 'X': { // ISO week-numbering year
                // Extension: The F&O spec says nothing about how to access the year associated with the week-of-the-year
                // e.g. Sat 1 Jan 2005 is in the 53rd week of 2004.
                // The 'W' component specifier gives 53, but 'Y' will give 2005.
                // I propose to add 'X' as the component specifier to give the ISO week-numbering year (2004 in this example)
                const thisYear = yearMonth(date.getUTCFullYear(), 0);
                const startOfISOYear = startOfFirstWeek(thisYear);
                const endOfISOYear = startOfFirstWeek(thisYear.nextYear());
                const now = date.getTime();
                if (now < startOfISOYear) {
                    componentValue = thisYear.year - 1;
                } else if (now >= endOfISOYear) {
                    componentValue = thisYear.year + 1;
                } else {
                    componentValue = thisYear.year;
                }
                break;
            }
            case 'x': { // ISO week-numbering month
                // Extension: The F&O spec says nothing about how to access the month associated with the week-of-the-month
                // e.g. Sat 1 Jan 2005 is in the 5th week of December 2004.
                // The 'w' component specifier gives 5, but 'W' will give January and 'Y' will give 2005.
                // I propose to add 'x' as the component specifier to give the 'week-numbering' month (December in this example)
                const thisMonth = yearMonth(date.getUTCFullYear(), date.getUTCMonth());
                const startOfISOMonth = startOfFirstWeek(thisMonth);
                const nextMonth = thisMonth.nextMonth();
                const endOfISOMonth = startOfFirstWeek(nextMonth);
                const now = date.getTime();
                if (now < startOfISOMonth) {
                    componentValue = thisMonth.previousMonth().month + 1;
                } else if (now >= endOfISOMonth) {
                    componentValue = nextMonth.month + 1;
                } else {
                    componentValue = thisMonth.month + 1;
                }
                break;
            }
            case 'H': // hour in day (24 hours)
                componentValue = date.getUTCHours();
                break;
            case 'h': // hour in half-day (12 hours)
                componentValue = date.getUTCHours();
                componentValue = componentValue % 12;
                if (componentValue === 0) {
                    componentValue = 12;
                }
                break;
            case 'P': // am/pm marker
                componentValue = date.getUTCHours() >= 12 ? 'pm' : 'am';
                break;
            case 'm': // minute in hour
                componentValue = date.getUTCMinutes();
                break;
            case 's': // second in minute
                componentValue = date.getUTCSeconds();
                break;
            case 'f': // fractional seconds
                componentValue = date.getUTCMilliseconds();
                break;
            case 'Z': // timezone
            case 'z':
                // since the date object is constructed from epoch millis, the TZ component is always be UTC.
                break;
            case 'C': // calendar name
                componentValue = 'ISO';
                break;
            case 'E': // era
                componentValue = 'ISO';
                break;
        }
        return componentValue;
    };

    let iso8601Spec = null;

    /**
     * formats the date/time as specified by the XPath fn:format-dateTime function
     * @param {number} millis - the timestamp to be formatted, in millis since the epoch
     * @param {string} picture - the picture string that specifies the format
     * @param {string} timezone - the timezone to use
     * @returns {string} - the formatted timestamp
     */
    function formatDateTime(millis, picture, timezone) {
        var offsetHours = 0;
        var offsetMinutes = 0;

        if (typeof timezone !== 'undefined') {
            // parse the hour and minute offsets
            // assume for now the format supplied is +hhmm
            const offset = parseInt(timezone);
            offsetHours = Math.floor(offset / 100);
            offsetMinutes = offset % 100;
        }

        var formatComponent = function (date, markerSpec) {
            var componentValue = getDateTimeFragment(date, markerSpec.component);

            // §9.8.4.3 Formatting Integer-Valued Date/Time Components
            if ('YMDdFWwXxHhms'.indexOf(markerSpec.component) !== -1) {
                if (markerSpec.component === 'Y') {
                    // §9.8.4.4 Formatting the Year Component
                    if (markerSpec.n !== -1) {
                        componentValue = componentValue % Math.pow(10, markerSpec.n);
                    }
                }
                if (markerSpec.names) {
                    if (markerSpec.component === 'M' || markerSpec.component === 'x') {
                        componentValue = months[componentValue - 1];
                    } else if (markerSpec.component === 'F') {
                        componentValue = days[componentValue];
                    } else {
                        throw {
                            code: 'D3133',
                            value: markerSpec.component
                        };
                    }
                    if (markerSpec.names === tcase.UPPER) {
                        componentValue = componentValue.toUpperCase();
                    } else if (markerSpec.names === tcase.LOWER) {
                        componentValue = componentValue.toLowerCase();
                    }
                    if (markerSpec.width && componentValue.length > markerSpec.width.max) {
                        componentValue = componentValue.substring(0, markerSpec.width.max);
                    }
                } else {
                    componentValue = _formatInteger(componentValue, markerSpec.integerFormat);
                }
            } else if (markerSpec.component === 'f') {
                // TODO §9.8.4.5 Formatting Fractional Seconds
                componentValue = _formatInteger(componentValue, markerSpec.integerFormat);
            } else if (markerSpec.component === 'Z' || markerSpec.component === 'z') {
                // §9.8.4.6 Formatting timezones
                const offset = offsetHours * 100 + offsetMinutes;
                if (markerSpec.integerFormat.regular) {
                    componentValue = _formatInteger(offset, markerSpec.integerFormat);
                } else {
                    const numDigits = markerSpec.integerFormat.mandatoryDigits;
                    if (numDigits === 1 || numDigits === 2) {
                        componentValue = _formatInteger(offsetHours, markerSpec.integerFormat);
                        if (offsetMinutes !== 0) {
                            componentValue += ':' + formatInteger(offsetMinutes, '00');
                        }
                    } else if (numDigits === 3 || numDigits === 4) {
                        componentValue = _formatInteger(offset, markerSpec.integerFormat);
                    } else {
                        throw {
                            code: 'D3134',
                            value: numDigits
                        };
                    }
                }
                if (offset >= 0) {
                    componentValue = '+' + componentValue;
                }
                if (markerSpec.component === 'z') {
                    componentValue = 'GMT' + componentValue;
                }
                if (offset === 0 && markerSpec.presentation2 === 't') {
                    componentValue = 'Z';
                }
            }
            return componentValue;
        };

        let formatSpec;
        if(typeof picture === 'undefined') {
            // default to ISO 8601 format
            if (iso8601Spec === null) {
                iso8601Spec = analyseDateTimePicture('[Y0001]-[M01]-[D01]T[H01]:[m01]:[s01].[f001][Z01:01t]');
            }
            formatSpec = iso8601Spec;
        } else {
            formatSpec = analyseDateTimePicture(picture);
        }

        const offsetMillis = (60 * offsetHours + offsetMinutes) * 60 * 1000;
        const dateTime = new Date(millis + offsetMillis);

        let result = '';
        formatSpec.parts.forEach(function (part) {
            if (part.type === 'literal') {
                result += part.value;
            } else {
                result += formatComponent(dateTime, part);
            }
        });

        return result;
    }

    /**
     * Generate a regex to parse integers or timestamps
     * @param {object} formatSpec - object representing the format
     * @returns {object} - regex
     */
    function generateRegex(formatSpec) {
        var matcher = {};
        if (formatSpec.type === 'datetime') {
            matcher.type = 'datetime';
            matcher.parts = formatSpec.parts.map(function (part) {
                var res = {};
                if (part.type === 'literal') {
                    res.regex = part.value.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
                } else if (part.component === 'Z' || part.component === 'z') {
                    // timezone
                    let separator;
                    if (!Array.isArray(part.integerFormat.groupingSeparators)) {
                        separator = part.integerFormat.groupingSeparators;
                    }
                    res.regex = '';
                    if (part.component === 'z') {
                        res.regex = 'GMT';
                    }
                    res.regex += '[-+][0-9]+';
                    if (separator) {
                        res.regex += separator.character + '[0-9]+';
                    }
                    res.parse = function(value) {
                        if (part.component === 'z') {
                            value = value.substring(3); // remove the leading GMT
                        }
                        let offsetHours = 0, offsetMinutes = 0;
                        if (separator) {
                            offsetHours = Number.parseInt(value.substring(0, value.indexOf(separator.character)));
                            offsetMinutes = Number.parseInt(value.substring(value.indexOf(separator.character) + 1));
                        } else {
                            // depends on number of digits
                            const numdigits = value.length - 1;
                            if (numdigits <= 2) {
                                // just hour offset
                                offsetHours = Number.parseInt(value);
                            } else {
                                offsetHours = Number.parseInt(value.substring(0, 3));
                                offsetMinutes = Number.parseInt(value.substring(3));
                            }
                        }
                        return offsetHours * 60 + offsetMinutes;
                    };
                } else if (part.integerFormat) {
                    res = generateRegex(part.integerFormat);
                } else {
                    // must be a month or day name
                    res.regex = '[a-zA-Z]+';
                    var lookup = {};
                    if (part.component === 'M' || part.component === 'x') {
                        // months
                        months.forEach(function (name, index) {
                            if (part.width && part.width.max) {
                                lookup[name.substring(0, part.width.max)] = index + 1;
                            } else {
                                lookup[name] = index + 1;
                            }
                        });
                    } else if (part.component === 'F') {
                        // days
                        days.forEach(function (name, index) {
                            if (index > 0) {
                                if (part.width && part.width.max) {
                                    lookup[name.substring(0, part.width.max)] = index;
                                } else {
                                    lookup[name] = index;
                                }
                            }
                        });
                    } else if (part.component === 'P') {
                        lookup = {'am': 0, 'AM': 0, 'pm': 1, 'PM': 1};
                    } else {
                        // unsupported 'name' option for this component
                        throw {
                            code: 'D3133',
                            value: part.component
                        };
                    }
                    res.parse = function (value) {
                        return lookup[value];
                    };
                }
                res.component = part.component;
                return res;
            });
        } else { // type === 'integer'
            matcher.type = 'integer';
            const isUpper = formatSpec.case === tcase.UPPER;
            switch (formatSpec.primary) {
                case formats.LETTERS:
                    matcher.regex = isUpper ? '[A-Z]+' : '[a-z]+';
                    matcher.parse = function (value) {
                        return lettersToDecimal(value, isUpper ? 'A' : 'a');
                    };
                    break;
                case formats.ROMAN:
                    matcher.regex = isUpper ? '[MDCLXVI]+' : '[mdclxvi]+';
                    matcher.parse = function (value) {
                        return romanToDecimal(isUpper ? value : value.toUpperCase());
                    };
                    break;
                case formats.WORDS:
                    matcher.regex = '(?:' + Object.keys(wordValues).concat('and', '[\\-, ]').join('|') + ')+';
                    matcher.parse = function (value) {
                        return wordsToNumber(value.toLowerCase());
                    };
                    break;
                case formats.DECIMAL:
                    matcher.regex = '[0-9]+';
                    if (formatSpec.ordinal) {
                        // ordinals
                        matcher.regex += '(?:th|st|nd|rd)';
                    }
                    matcher.parse = function (value) {
                        let digits = value;
                        if (formatSpec.ordinal) {
                            // strip off the suffix
                            digits = value.substring(0, value.length - 2);
                        }
                        // strip out the separators
                        if (formatSpec.regular) {
                            digits = digits.split(',').join('');
                        } else {
                            formatSpec.groupingSeparators.forEach(sep => {
                                digits = digits.split(sep.character).join('');
                            });
                        }
                        if (formatSpec.zeroCode !== 0x30) {
                            // apply offset
                            digits = digits.split('').map(char => String.fromCodePoint(char.codePointAt(0) - formatSpec.zeroCode + 0x30)).join('');
                        }
                        return parseInt(digits);
                    };
                    break;
                case formats.SEQUENCE:
                    throw {
                        code: 'D3130',
                        value: formatSpec.token
                    };
            }

        }
        return matcher;
    }

    /**
     * parse a string containing an integer as specified by the picture string
     * @param {string} value - the string to parse
     * @param {string} picture - the picture string
     * @returns {number} - the parsed number
     */
    function parseInteger(value, picture) {
        if (typeof value === 'undefined') {
            return undefined;
        }

        const formatSpec = analyseIntegerPicture(picture);
        const matchSpec = generateRegex(formatSpec);
        //const fullRegex = '^' + matchSpec.regex + '$';
        //const matcher = new RegExp(fullRegex);
        // TODO validate input based on the matcher regex
        const result = matchSpec.parse(value);
        return result;
    }

    /**
     * parse a string containing a timestamp as specified by the picture string
     * @param {string} timestamp - the string to parse
     * @param {string} picture - the picture string
     * @returns {number} - the parsed timestamp in millis since the epoch
     */
    function parseDateTime(timestamp, picture) {
        const formatSpec = analyseDateTimePicture(picture);
        const matchSpec = generateRegex(formatSpec);
        const fullRegex = '^' + matchSpec.parts.map(part => '(' + part.regex + ')').join('') + '$';

        const matcher = new RegExp(fullRegex, 'i'); // TODO can cache this against the picture
        var info = matcher.exec(timestamp);
        if (info !== null) {
            // validate what we've just parsed - do we have enough information to create a timestamp?
            // rules:
            // The date is specified by one of:
            //    {Y, M, D}    (dateA)
            // or {Y, d}       (dateB)
            // or {Y, x, w, F} (dateC)
            // or {X, W, F}    (dateD)
            // The time is specified by one of:
            //    {H, m, s, f}    (timeA)
            // or {P, h, m, s, f} (timeB)
            // All sets can have an optional Z
            // To create a timestamp (epoch millis) we need both date and time, but we can default missing
            // information according to the following rules:
            // - line up one combination of the above from date, and one from time, most significant value (MSV) to least significant (LSV
            // - for the values that have been captured, if there are any gaps between MSV and LSV, then throw an error
            //     (e.g.) if hour and seconds, but not minutes is given - throw
            //     (e.g.) if month, hour and minutes, but not day-of-month is given - throw
            // - anything right of the LSV should be defaulted to zero
            //     (e.g.) if hour and minutes given, default seconds and fractional seconds to zero
            //     (e.g.) if date only given, default the time to 0:00:00.000 (midnight)
            // - anything left of the MSV should be defaulted to the value of that component returned by $now()
            //     (e.g.) if time only given, default the date to today
            //     (e.g.) if month and date given, default to this year (and midnight, by previous rule)
            //   -- default values for X, x, W, w, F will be derived from the values returned by $now()

            // implement the above rules
            // determine which of the above date/time combinations we have by using bit masks

            //        Y X M x W w d D F P H h m s f Z
            // dateA  1 0 1 0 0 0 0 1 ?                     0 - must not appear
            // dateB  1 0 0 0 0 0 1 0 ?                     1 - can appear - relevant
            // dateC  0 1 0 1 0 1 0 0 1                     ? - can appear - ignored
            // dateD  0 1 0 0 1 0 0 0 1
            // timeA                    0 1 0 1 1 1
            // timeB                    1 0 1 1 1 1

            // create bitmasks based on the above
            //    date mask             YXMxWwdD
            const dmA = 161;  // binary 10100001
            const dmB = 130;  // binary 10000010
            const dmC = 84;   // binary 01010100
            const dmD = 72;   // binary 01001000
            //    time mask             PHhmsf
            const tmA = 23;   // binary 010111
            const tmB = 47;   // binary 101111

            const components = {};
            for (let i = 1; i < info.length; i++) {
                const mpart = matchSpec.parts[i - 1];
                if (mpart.parse) {
                    components[mpart.component] = mpart.parse(info[i]);
                }
            }

            if(Object.getOwnPropertyNames(components).length === 0) {
                // nothing specified
                return undefined;
            }

            let mask = 0;

            const shift = bit => {
                mask <<= 1;
                mask += bit ? 1 : 0;
            };

            const isType = type => {
                // shouldn't match any 0's, must match at least one 1
                return !(~type & mask) && !!(type & mask);
            };

            'YXMxWwdD'.split('').forEach(part => shift(components[part]));

            const dateA = isType(dmA);
            const dateB = !dateA && isType(dmB);
            const dateC = isType(dmC);
            const dateD = !dateC && isType(dmD);

            mask = 0;
            'PHhmsf'.split('').forEach(part => shift(components[part]));

            const timeA = isType(tmA);
            const timeB = !timeA && isType(tmB);

            // should only be zero or one date type and zero or one time type

            const dateComps = dateB ? 'YD' : dateC ? 'XxwF' : dateD? 'XWF' : 'YMD';
            const timeComps = timeB ? 'Phmsf' : 'Hmsf';

            const comps = dateComps + timeComps;

            // step through the candidate parts from most significant to least significant
            // default the most significant unspecified parts to current timestamp component
            // default the least significant unspecified parts to zero
            // if any gaps in between the specified parts, throw an error

            const now = this.environment.timestamp; // must get the fixed timestamp from jsonata

            let startSpecified = false;
            let endSpecified = false;
            comps.split('').forEach(part => {
                if(typeof components[part] === 'undefined') {
                    if(startSpecified) {
                        // past the specified block - default to zero
                        components[part] = ('MDd'.indexOf(part) !== -1) ? 1 : 0;
                        endSpecified = true;
                    } else {
                        // haven't hit the specified block yet, default to current timestamp
                        components[part] = getDateTimeFragment(now, part);
                    }
                } else {
                    startSpecified = true;
                    if(endSpecified) {
                        throw {
                            code: 'D3136'
                        };
                    }
                }
            });

            // validate and fill in components
            if (components.M > 0) {
                components.M -= 1;  // Date.UTC requires a zero-indexed month
            } else {
                components.M = 0; // default to January
            }
            if (dateB) {
                // millis for given 1st Jan of that year (at 00:00 UTC)
                const firstJan = Date.UTC(components.Y, 0);
                const offsetMillis = (components.d - 1) * 1000 * 60 * 60 * 24;
                const derivedDate = new Date(firstJan + offsetMillis);
                components.M = derivedDate.getUTCMonth();
                components.D = derivedDate.getUTCDate();
            }
            if (dateC) {
                // TODO implement this
                // parsing this format not currently supported
                throw {
                    code: 'D3136'
                };
            }
            if (dateD) {
                // TODO implement this
                // parsing this format (ISO week date) not currently supported
                throw {
                    code: 'D3136'
                };
            }
            if (timeB) {
                // 12hr to 24hr
                components.H = components.h === 12 ? 0 : components.h;
                if (components.P === 1) {
                    components.H += 12;
                }
            }

            var millis = Date.UTC(components.Y, components.M, components.D, components.H, components.m, components.s, components.f);
            if(components.Z || components.z) {
                // adjust for timezone
                millis -= (components.Z || components.z) * 60 * 1000;
            }
            return millis;
        }
    }

    // Regular expression to match an ISO 8601 formatted timestamp
    var iso8601regex = new RegExp('^\\d{4}(-[01]\\d)*(-[0-3]\\d)*(T[0-2]\\d:[0-5]\\d:[0-5]\\d)*(\\.\\d+)?([+-][0-2]\\d:?[0-5]\\d|Z)?$');

    /**
     * Converts an ISO 8601 timestamp to milliseconds since the epoch
     *
     * @param {string} timestamp - the timestamp to be converted
     * @param {string} [picture] - the picture string defining the format of the timestamp (defaults to ISO 8601)
     * @returns {Number} - milliseconds since the epoch
     */
    function toMillis(timestamp, picture) {
        // undefined inputs always return undefined
        if(typeof timestamp === 'undefined') {
            return undefined;
        }

        if(typeof picture === 'undefined') {
            if (!iso8601regex.test(timestamp)) {
                throw {
                    stack: (new Error()).stack,
                    code: "D3110",
                    value: timestamp
                };
            }

            return Date.parse(timestamp);
        } else {
            return parseDateTime.call(this, timestamp, picture);
        }
    }

    /**
     * Converts milliseconds since the epoch to an ISO 8601 timestamp
     * @param {Number} millis - milliseconds since the epoch to be converted
     * @param {string} [picture] - the picture string defining the format of the timestamp (defaults to ISO 8601)
     * @param {string} [timezone] - the timezone to format the timestamp in (defaults to UTC)
     * @returns {String} - the formatted timestamp
     */
    function fromMillis(millis, picture, timezone) {
        // undefined inputs always return undefined
        if(typeof millis === 'undefined') {
            return undefined;
        }

        return formatDateTime.call(this, millis, picture, timezone);
    }

    return {
        formatInteger, parseInteger, fromMillis, toMillis
    };
})();

module.exports = dateTime;

},{"./utils":7}],3:[function(require,module,exports){
(function (global){(function (){
/**
 * © Copyright IBM Corp. 2016, 2018 All Rights Reserved
 *   Project name: JSONata
 *   This project is licensed under the MIT License, see LICENSE
 */

var utils = require('./utils');
var deepmerger = require('deepmerge');

const functions = (() => {
    'use strict';

    var isNumeric = utils.isNumeric;
    var isArrayOfStrings = utils.isArrayOfStrings;
    var isArrayOfNumbers = utils.isArrayOfNumbers;
    var createSequence = utils.createSequence;
    var isSequence = utils.isSequence;
    var isFunction = utils.isFunction;
    var isLambda = utils.isLambda;
    var isIterable = utils.isIterable;
    var getFunctionArity = utils.getFunctionArity;
    var deepEquals = utils.isDeepEqual;
    var stringToArray = utils.stringToArray;

    /**
     * Sum function
     * @param {Object} args - Arguments
     * @returns {number} Total value of arguments
     */
    function sum(args) {
        // undefined inputs always return undefined
        if (typeof args === 'undefined') {
            return undefined;
        }

        var total = 0;
        args.forEach(function (num) {
            total += num;
        });
        return total;
    }

    /**
     * Count function
     * @param {Object} args - Arguments
     * @returns {number} Number of elements in the array
     */
    function count(args) {
        // undefined inputs always return undefined
        if (typeof args === 'undefined') {
            return 0;
        }

        return args.length;
    }

    /**
     * Max function
     * @param {Object} args - Arguments
     * @returns {number} Max element in the array
     */
    function max(args) {
        // undefined inputs always return undefined
        if (typeof args === 'undefined' || args.length === 0) {
            return undefined;
        }

        return Math.max.apply(Math, args);
    }

    /**
     * Min function
     * @param {Object} args - Arguments
     * @returns {number} Min element in the array
     */
    function min(args) {
        // undefined inputs always return undefined
        if (typeof args === 'undefined' || args.length === 0) {
            return undefined;
        }

        return Math.min.apply(Math, args);
    }

    /**
     * Average function
     * @param {Object} args - Arguments
     * @returns {number} Average element in the array
     */
    function average(args) {
        // undefined inputs always return undefined
        if (typeof args === 'undefined' || args.length === 0) {
            return undefined;
        }

        var total = 0;
        args.forEach(function (num) {
            total += num;
        });
        return total / args.length;
    }

    /**
     * Stringify arguments
     * @param {Object} arg - Arguments
     * @param {boolean} [prettify] - Pretty print the result
     * @returns {String} String from arguments
     */
    function string(arg, prettify = false) {
        // undefined inputs always return undefined
        if (typeof arg === 'undefined') {
            return undefined;
        }

        var str;

        if (typeof arg === 'string') {
            // already a string
            str = arg;
        } else if (isFunction(arg)) {
            // functions (built-in and lambda convert to empty string
            str = '';
        } else if (typeof arg === 'number' && !isFinite(arg)) {
            throw {
                code: "D3001",
                value: arg,
                stack: (new Error()).stack
            };
        } else {
            var space = prettify ? 2 : 0;
            if(Array.isArray(arg) && arg.outerWrapper) {
                arg = arg[0];
            }
            str = JSON.stringify(arg, function (key, val) {
                return (typeof val !== 'undefined' && val !== null && val.toPrecision && isNumeric(val)) ? Number(val.toPrecision(15)) :
                    (val && isFunction(val)) ? '' : val;
            }, space);
        }
        return str;
    }

    /**
     * Create substring based on character number and length
     * @param {String} str - String to evaluate
     * @param {Integer} start - Character number to start substring
     * @param {Integer} [length] - Number of characters in substring
     * @returns {string|*} Substring
     */
    function substring(str, start, length) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        var strArray = stringToArray(str);
        var strLength = strArray.length;

        if (strLength + start < 0) {
            start = 0;
        }

        if (typeof length !== 'undefined') {
            if (length <= 0) {
                return '';
            }
            var end = start >= 0 ? start + length : strLength + start + length;
            return strArray.slice(start, end).join('');
        }

        return strArray.slice(start).join('');
    }

    /**
     * Create substring up until a character
     * @param {String} str - String to evaluate
     * @param {String} chars - Character to define substring boundary
     * @returns {*} Substring
     */
    function substringBefore(str, chars) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        var pos = str.indexOf(chars);
        if (pos > -1) {
            return str.substr(0, pos);
        } else {
            return str;
        }
    }

    /**
     * Create substring after a character
     * @param {String} str - String to evaluate
     * @param {String} chars - Character to define substring boundary
     * @returns {*} Substring
     */
    function substringAfter(str, chars) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        var pos = str.indexOf(chars);
        if (pos > -1) {
            return str.substr(pos + chars.length);
        } else {
            return str;
        }
    }

    /**
     * Lowercase a string
     * @param {String} str - String to evaluate
     * @returns {string} Lowercase string
     */
    function lowercase(str) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        return str.toLowerCase();
    }

    /**
     * Uppercase a string
     * @param {String} str - String to evaluate
     * @returns {string} Uppercase string
     */
    function uppercase(str) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        return str.toUpperCase();
    }

    /**
     * length of a string
     * @param {String} str - string
     * @returns {Number} The number of characters in the string
     */
    function length(str) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        return stringToArray(str).length;
    }

    /**
     * Normalize and trim whitespace within a string
     * @param {string} str - string to be trimmed
     * @returns {string} - trimmed string
     */
    function trim(str) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        // normalize whitespace
        var result = str.replace(/[ \t\n\r]+/gm, ' ');
        if (result.charAt(0) === ' ') {
            // strip leading space
            result = result.substring(1);
        }
        if (result.charAt(result.length - 1) === ' ') {
            // strip trailing space
            result = result.substring(0, result.length - 1);
        }
        return result;
    }

    /**
     * Pad a string to a minimum width by adding characters to the start or end
     * @param {string} str - string to be padded
     * @param {number} width - the minimum width; +ve pads to the right, -ve pads to the left
     * @param {string} [char] - the pad character(s); defaults to ' '
     * @returns {string} - padded string
     */
    function pad(str, width, char) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        if (typeof char === 'undefined' || char.length === 0) {
            char = ' ';
        }

        var result;
        var padLength = Math.abs(width) - length(str);
        if (padLength > 0) {
            var padding = (new Array(padLength + 1)).join(char);
            if (char.length > 1) {
                padding = substring(padding, 0, padLength);
            }
            if (width > 0) {
                result = str + padding;
            } else {
                result = padding + str;
            }
        } else {
            result = str;
        }
        return result;
    }

    /**
     * Evaluate the matcher function against the str arg
     *
     * @param {*} matcher - matching function (native or lambda)
     * @param {string} str - the string to match against
     * @returns {object} - structure that represents the match(es)
     */
    function* evaluateMatcher(matcher, str) {
        var result = matcher.apply(this, [str]); // eslint-disable-line no-useless-call
        if(isIterable(result)) {
            result = yield * result;
        }
        if(result && !(typeof result.start === 'number' || result.end === 'number' || Array.isArray(result.groups) || isFunction(result.next))) {
            // the matcher function didn't return the correct structure
            throw {
                code: "T1010",
                stack: (new Error()).stack,
            };
        }
        return result;
    }

    /**
     * Tests if the str contains the token
     * @param {String} str - string to test
     * @param {String} token - substring or regex to find
     * @returns {Boolean} - true if str contains token
     */
    function* contains(str, token) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        var result;

        if (typeof token === 'string') {
            result = (str.indexOf(token) !== -1);
        } else {
            var matches = yield* evaluateMatcher(token, str);
            result = (typeof matches !== 'undefined');
        }

        return result;
    }

    /**
     * Match a string with a regex returning an array of object containing details of each match
     * @param {String} str - string
     * @param {String} regex - the regex applied to the string
     * @param {Integer} [limit] - max number of matches to return
     * @returns {Array} The array of match objects
     */
    function* match(str, regex, limit) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        // limit, if specified, must be a non-negative number
        if (limit < 0) {
            throw {
                stack: (new Error()).stack,
                value: limit,
                code: 'D3040',
                index: 3
            };
        }

        var result = createSequence();

        if (typeof limit === 'undefined' || limit > 0) {
            var count = 0;
            var matches = yield* evaluateMatcher(regex, str);
            if (typeof matches !== 'undefined') {
                while (typeof matches !== 'undefined' && (typeof limit === 'undefined' || count < limit)) {
                    result.push({
                        match: matches.match,
                        index: matches.start,
                        groups: matches.groups
                    });
                    matches = yield* evaluateMatcher(matches.next);
                    count++;
                }
            }
        }

        return result;
    }

    /**
     * Match a string with a regex returning an array of object containing details of each match
     * @param {String} str - string
     * @param {String} pattern - the substring/regex applied to the string
     * @param {String} replacement - text to replace the matched substrings
     * @param {Integer} [limit] - max number of matches to return
     * @returns {Array} The array of match objects
     */
    function* replace(str, pattern, replacement, limit) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        var self = this;

        // pattern cannot be an empty string
        if (pattern === '') {
            throw {
                code: "D3010",
                stack: (new Error()).stack,
                value: pattern,
                index: 2
            };
        }

        // limit, if specified, must be a non-negative number
        if (limit < 0) {
            throw {
                code: "D3011",
                stack: (new Error()).stack,
                value: limit,
                index: 4
            };
        }

        var replacer;
        if (typeof replacement === 'string') {
            replacer = function (regexMatch) {
                var substitute = '';
                // scan forward, copying the replacement text into the substitute string
                // and replace any occurrence of $n with the values matched by the regex
                var position = 0;
                var index = replacement.indexOf('$', position);
                while (index !== -1 && position < replacement.length) {
                    substitute += replacement.substring(position, index);
                    position = index + 1;
                    var dollarVal = replacement.charAt(position);
                    if (dollarVal === '$') {
                        // literal $
                        substitute += '$';
                        position++;
                    } else if (dollarVal === '0') {
                        substitute += regexMatch.match;
                        position++;
                    } else {
                        var maxDigits;
                        if (regexMatch.groups.length === 0) {
                            // no sub-matches; any $ followed by a digit will be replaced by an empty string
                            maxDigits = 1;
                        } else {
                            // max number of digits to parse following the $
                            maxDigits = Math.floor(Math.log(regexMatch.groups.length) * Math.LOG10E) + 1;
                        }
                        index = parseInt(replacement.substring(position, position + maxDigits), 10);
                        if (maxDigits > 1 && index > regexMatch.groups.length) {
                            index = parseInt(replacement.substring(position, position + maxDigits - 1), 10);
                        }
                        if (!isNaN(index)) {
                            if (regexMatch.groups.length > 0) {
                                var submatch = regexMatch.groups[index - 1];
                                if (typeof submatch !== 'undefined') {
                                    substitute += submatch;
                                }
                            }
                            position += index.toString().length;
                        } else {
                            // not a capture group, treat the $ as literal
                            substitute += '$';
                        }
                    }
                    index = replacement.indexOf('$', position);
                }
                substitute += replacement.substring(position);
                return substitute;
            };
        } else {
            replacer = replacement;
        }

        var result = '';
        var position = 0;

        if (typeof limit === 'undefined' || limit > 0) {
            var count = 0;
            if (typeof pattern === 'string') {
                var index = str.indexOf(pattern, position);
                while (index !== -1 && (typeof limit === 'undefined' || count < limit)) {
                    result += str.substring(position, index);
                    result += replacement;
                    position = index + pattern.length;
                    count++;
                    index = str.indexOf(pattern, position);
                }
                result += str.substring(position);
            } else {
                var matches = yield* evaluateMatcher(pattern, str);
                if (typeof matches !== 'undefined') {
                    while (typeof matches !== 'undefined' && (typeof limit === 'undefined' || count < limit)) {
                        result += str.substring(position, matches.start);
                        var replacedWith = replacer.apply(self, [matches]);
                        if (isIterable(replacedWith)) {
                            replacedWith = yield* replacedWith;
                        }
                        // check replacedWith is a string
                        if (typeof replacedWith === 'string') {
                            result += replacedWith;
                        } else {
                            // not a string - throw error
                            throw {
                                code: "D3012",
                                stack: (new Error()).stack,
                                value: replacedWith
                            };
                        }
                        position = matches.start + matches.match.length;
                        count++;
                        matches = yield* evaluateMatcher(matches.next);
                    }
                    result += str.substring(position);
                } else {
                    result = str;
                }
            }
        } else {
            result = str;
        }

        return result;
    }

    /**
     * Base64 encode a string
     * @param {String} str - string
     * @returns {String} Base 64 encoding of the binary data
     */
    function base64encode(str) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }
        // Use btoa in a browser, or Buffer in Node.js

        var btoa = typeof window !== 'undefined' ?
            /* istanbul ignore next */ window.btoa :
            function (str) {
                // Simply doing `new Buffer` at this point causes Browserify to pull
                // in the entire Buffer browser library, which is large and unnecessary.
                // Using `global.Buffer` defeats this.
                return new global.Buffer.from(str, 'binary').toString('base64'); // eslint-disable-line new-cap
            };
        return btoa(str);
    }

    /**
     * Base64 decode a string
     * @param {String} str - string
     * @returns {String} Base 64 encoding of the binary data
     */
    function base64decode(str) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }
        // Use btoa in a browser, or Buffer in Node.js
        var atob = typeof window !== 'undefined' ?
            /* istanbul ignore next */ window.atob :
            function (str) {
                // Simply doing `new Buffer` at this point causes Browserify to pull
                // in the entire Buffer browser library, which is large and unnecessary.
                // Using `global.Buffer` defeats this.
                return new global.Buffer(str, 'base64').toString('binary');
            };
        return atob(str);
    }

    /**
     * Encode a string into a component for a url
     * @param {String} str - String to encode
     * @returns {string} Encoded string
     */
    function encodeUrlComponent(str) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        // Catch URIErrors when URI sequence is malformed
        var returnVal;
        try {
            returnVal = encodeURIComponent(str);
        } catch (e) {
            throw {
                code: "D3140",
                stack: (new Error()).stack,
                value: str,
                functionName: "encodeUrlComponent"
            };
        }
        return returnVal;
    }

    /**
     * Encode a string into a url
     * @param {String} str - String to encode
     * @returns {string} Encoded string
     */
    function encodeUrl(str) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        // Catch URIErrors when URI sequence is malformed
        var returnVal;
        try {
            returnVal = encodeURI(str);
        } catch (e) {
            throw {
                code: "D3140",
                stack: (new Error()).stack,
                value: str,
                functionName: "encodeUrl"
            };
        }
        return returnVal;
    }

    /**
     * Decode a string from a component for a url
     * @param {String} str - String to decode
     * @returns {string} Decoded string
     */
    function decodeUrlComponent(str) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        // Catch URIErrors when URI sequence is malformed
        var returnVal;
        try {
            returnVal = decodeURIComponent(str);
        } catch (e) {
            throw {
                code: "D3140",
                stack: (new Error()).stack,
                value: str,
                functionName: "decodeUrlComponent"
            };
        }
        return returnVal;
    }

    /**
     * Decode a string from a url
     * @param {String} str - String to decode
     * @returns {string} Decoded string
     */
    function decodeUrl(str) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        // Catch URIErrors when URI sequence is malformed
        var returnVal;
        try {
            returnVal = decodeURI(str);
        } catch (e) {
            throw {
                code: "D3140",
                stack: (new Error()).stack,
                value: str,
                functionName: "decodeUrl"
            };
        }
        return returnVal;
    }

    /**
     * Split a string into an array of substrings
     * @param {String} str - string
     * @param {String} separator - the token or regex that splits the string
     * @param {Integer} [limit] - max number of substrings
     * @returns {Array} The array of string
     */
    function* split(str, separator, limit) {
        // undefined inputs always return undefined
        if (typeof str === 'undefined') {
            return undefined;
        }

        // limit, if specified, must be a non-negative number
        if (limit < 0) {
            throw {
                code: "D3020",
                stack: (new Error()).stack,
                value: limit,
                index: 3
            };
        }

        var result = [];

        if (typeof limit === 'undefined' || limit > 0) {
            if (typeof separator === 'string') {
                result = str.split(separator, limit);
            } else {
                var count = 0;
                var matches = yield* evaluateMatcher(separator, str);
                if (typeof matches !== 'undefined') {
                    var start = 0;
                    while (typeof matches !== 'undefined' && (typeof limit === 'undefined' || count < limit)) {
                        result.push(str.substring(start, matches.start));
                        start = matches.end;
                        matches = yield* evaluateMatcher(matches.next);
                        count++;
                    }
                    if (typeof limit === 'undefined' || count < limit) {
                        result.push(str.substring(start));
                    }
                } else {
                    result.push(str);
                }
            }
        }

        return result;
    }

    /**
     * Join an array of strings
     * @param {Array} strs - array of string
     * @param {String} [separator] - the token that splits the string
     * @returns {String} The concatenated string
     */
    function join(strs, separator) {
        // undefined inputs always return undefined
        if (typeof strs === 'undefined') {
            return undefined;
        }

        // if separator is not specified, default to empty string
        if (typeof separator === 'undefined') {
            separator = "";
        }

        return strs.join(separator);
    }

    /**
     * Formats a number into a decimal string representation using XPath 3.1 F&O fn:format-number spec
     * @param {number} value - number to format
     * @param {String} picture - picture string definition
     * @param {Object} [options] - override locale defaults
     * @returns {String} The formatted string
     */
    function formatNumber(value, picture, options) {
        // undefined inputs always return undefined
        if (typeof value === 'undefined') {
            return undefined;
        }

        var defaults = {
            "decimal-separator": ".",
            "grouping-separator": ",",
            "exponent-separator": "e",
            "infinity": "Infinity",
            "minus-sign": "-",
            "NaN": "NaN",
            "percent": "%",
            "per-mille": "\u2030",
            "zero-digit": "0",
            "digit": "#",
            "pattern-separator": ";"
        };

        // if `options` is specified, then its entries override defaults
        var properties = defaults;
        if (typeof options !== 'undefined') {
            Object.keys(options).forEach(function (key) {
                properties[key] = options[key];
            });
        }

        var decimalDigitFamily = [];
        var zeroCharCode = properties['zero-digit'].charCodeAt(0);
        for (var ii = zeroCharCode; ii < zeroCharCode + 10; ii++) {
            decimalDigitFamily.push(String.fromCharCode(ii));
        }

        var activeChars = decimalDigitFamily.concat([properties['decimal-separator'], properties['exponent-separator'], properties['grouping-separator'], properties.digit, properties['pattern-separator']]);

        var subPictures = picture.split(properties['pattern-separator']);

        if (subPictures.length > 2) {
            throw {
                code: 'D3080',
                stack: (new Error()).stack
            };
        }

        var splitParts = function (subpicture) {
            var prefix = (function () {
                var ch;
                for (var ii = 0; ii < subpicture.length; ii++) {
                    ch = subpicture.charAt(ii);
                    if (activeChars.indexOf(ch) !== -1 && ch !== properties['exponent-separator']) {
                        return subpicture.substring(0, ii);
                    }
                }
            })();
            var suffix = (function () {
                var ch;
                for (var ii = subpicture.length - 1; ii >= 0; ii--) {
                    ch = subpicture.charAt(ii);
                    if (activeChars.indexOf(ch) !== -1 && ch !== properties['exponent-separator']) {
                        return subpicture.substring(ii + 1);
                    }
                }
            })();
            var activePart = subpicture.substring(prefix.length, subpicture.length - suffix.length);
            var mantissaPart, exponentPart, integerPart, fractionalPart;
            var exponentPosition = subpicture.indexOf(properties['exponent-separator'], prefix.length);
            if (exponentPosition === -1 || exponentPosition > subpicture.length - suffix.length) {
                mantissaPart = activePart;
                exponentPart = undefined;
            } else {
                mantissaPart = activePart.substring(0, exponentPosition);
                exponentPart = activePart.substring(exponentPosition + 1);
            }
            var decimalPosition = mantissaPart.indexOf(properties['decimal-separator']);
            if (decimalPosition === -1) {
                integerPart = mantissaPart;
                fractionalPart = suffix;
            } else {
                integerPart = mantissaPart.substring(0, decimalPosition);
                fractionalPart = mantissaPart.substring(decimalPosition + 1);
            }
            return {
                prefix: prefix,
                suffix: suffix,
                activePart: activePart,
                mantissaPart: mantissaPart,
                exponentPart: exponentPart,
                integerPart: integerPart,
                fractionalPart: fractionalPart,
                subpicture: subpicture
            };
        };

        // validate the picture string, F&O 4.7.3
        var validate = function (parts) {
            var error;
            var ii;
            var subpicture = parts.subpicture;
            var decimalPos = subpicture.indexOf(properties['decimal-separator']);
            if (decimalPos !== subpicture.lastIndexOf(properties['decimal-separator'])) {
                error = 'D3081';
            }
            if (subpicture.indexOf(properties.percent) !== subpicture.lastIndexOf(properties.percent)) {
                error = 'D3082';
            }
            if (subpicture.indexOf(properties['per-mille']) !== subpicture.lastIndexOf(properties['per-mille'])) {
                error = 'D3083';
            }
            if (subpicture.indexOf(properties.percent) !== -1 && subpicture.indexOf(properties['per-mille']) !== -1) {
                error = 'D3084';
            }
            var valid = false;
            for (ii = 0; ii < parts.mantissaPart.length; ii++) {
                var ch = parts.mantissaPart.charAt(ii);
                if (decimalDigitFamily.indexOf(ch) !== -1 || ch === properties.digit) {
                    valid = true;
                    break;
                }
            }
            if (!valid) {
                error = 'D3085';
            }
            var charTypes = parts.activePart.split('').map(function (char) {
                return activeChars.indexOf(char) === -1 ? 'p' : 'a';
            }).join('');
            if (charTypes.indexOf('p') !== -1) {
                error = 'D3086';
            }
            if (decimalPos !== -1) {
                if (subpicture.charAt(decimalPos - 1) === properties['grouping-separator'] || subpicture.charAt(decimalPos + 1) === properties['grouping-separator']) {
                    error = 'D3087';
                }
            } else if (parts.integerPart.charAt(parts.integerPart.length - 1) === properties['grouping-separator']) {
                error = 'D3088';
            }
            if (subpicture.indexOf(properties['grouping-separator'] + properties['grouping-separator']) !== -1) {
                error = 'D3089';
            }
            var optionalDigitPos = parts.integerPart.indexOf(properties.digit);
            if (optionalDigitPos !== -1 && parts.integerPart.substring(0, optionalDigitPos).split('').filter(function (char) {
                return decimalDigitFamily.indexOf(char) > -1;
            }).length > 0) {
                error = 'D3090';
            }
            optionalDigitPos = parts.fractionalPart.lastIndexOf(properties.digit);
            if (optionalDigitPos !== -1 && parts.fractionalPart.substring(optionalDigitPos).split('').filter(function (char) {
                return decimalDigitFamily.indexOf(char) > -1;
            }).length > 0) {
                error = 'D3091';
            }
            var exponentExists = (typeof parts.exponentPart === 'string');
            if (exponentExists && parts.exponentPart.length > 0 && (subpicture.indexOf(properties.percent) !== -1 || subpicture.indexOf(properties['per-mille']) !== -1)) {
                error = 'D3092';
            }
            if (exponentExists && (parts.exponentPart.length === 0 || parts.exponentPart.split('').filter(function (char) {
                return decimalDigitFamily.indexOf(char) === -1;
            }).length > 0)) {
                error = 'D3093';
            }
            if (error) {
                throw {
                    code: error,
                    stack: (new Error()).stack
                };
            }
        };

        // analyse the picture string, F&O 4.7.4
        var analyse = function (parts) {
            var getGroupingPositions = function (part, toLeft) {
                var positions = [];
                var groupingPosition = part.indexOf(properties['grouping-separator']);
                while (groupingPosition !== -1) {
                    var charsToTheRight = (toLeft ? part.substring(0, groupingPosition) : part.substring(groupingPosition)).split('').filter(function (char) {
                        return decimalDigitFamily.indexOf(char) !== -1 || char === properties.digit;
                    }).length;
                    positions.push(charsToTheRight);
                    groupingPosition = parts.integerPart.indexOf(properties['grouping-separator'], groupingPosition + 1);
                }
                return positions;
            };
            var integerPartGroupingPositions = getGroupingPositions(parts.integerPart);
            var regular = function (indexes) {
                // are the grouping positions regular? i.e. same interval between each of them
                if (indexes.length === 0) {
                    return 0;
                }
                var gcd = function (a, b) {
                    return b === 0 ? a : gcd(b, a % b);
                };
                // find the greatest common divisor of all the positions
                var factor = indexes.reduce(gcd);
                // is every position separated by this divisor? If so, it's regular
                for (var index = 1; index <= indexes.length; index++) {
                    if (indexes.indexOf(index * factor) === -1) {
                        return 0;
                    }
                }
                return factor;
            };

            var regularGrouping = regular(integerPartGroupingPositions);
            var fractionalPartGroupingPositions = getGroupingPositions(parts.fractionalPart, true);

            var minimumIntegerPartSize = parts.integerPart.split('').filter(function (char) {
                return decimalDigitFamily.indexOf(char) !== -1;
            }).length;
            var scalingFactor = minimumIntegerPartSize;

            var fractionalPartArray = parts.fractionalPart.split('');
            var minimumFactionalPartSize = fractionalPartArray.filter(function (char) {
                return decimalDigitFamily.indexOf(char) !== -1;
            }).length;
            var maximumFactionalPartSize = fractionalPartArray.filter(function (char) {
                return decimalDigitFamily.indexOf(char) !== -1 || char === properties.digit;
            }).length;
            var exponentPresent = typeof parts.exponentPart === 'string';
            if (minimumIntegerPartSize === 0 && maximumFactionalPartSize === 0) {
                if (exponentPresent) {
                    minimumFactionalPartSize = 1;
                    maximumFactionalPartSize = 1;
                } else {
                    minimumIntegerPartSize = 1;
                }
            }
            if (exponentPresent && minimumIntegerPartSize === 0 && parts.integerPart.indexOf(properties.digit) !== -1) {
                minimumIntegerPartSize = 1;
            }
            if (minimumIntegerPartSize === 0 && minimumFactionalPartSize === 0) {
                minimumFactionalPartSize = 1;
            }
            var minimumExponentSize = 0;
            if (exponentPresent) {
                minimumExponentSize = parts.exponentPart.split('').filter(function (char) {
                    return decimalDigitFamily.indexOf(char) !== -1;
                }).length;
            }

            return {
                integerPartGroupingPositions: integerPartGroupingPositions,
                regularGrouping: regularGrouping,
                minimumIntegerPartSize: minimumIntegerPartSize,
                scalingFactor: scalingFactor,
                prefix: parts.prefix,
                fractionalPartGroupingPositions: fractionalPartGroupingPositions,
                minimumFactionalPartSize: minimumFactionalPartSize,
                maximumFactionalPartSize: maximumFactionalPartSize,
                minimumExponentSize: minimumExponentSize,
                suffix: parts.suffix,
                picture: parts.subpicture
            };
        };

        var parts = subPictures.map(splitParts);
        parts.forEach(validate);

        var variables = parts.map(analyse);

        var minus_sign = properties['minus-sign'];
        var zero_digit = properties['zero-digit'];
        var decimal_separator = properties['decimal-separator'];
        var grouping_separator = properties['grouping-separator'];

        if (variables.length === 1) {
            variables.push(JSON.parse(JSON.stringify(variables[0])));
            variables[1].prefix = minus_sign + variables[1].prefix;
        }

        // TODO cache the result of the analysis

        // format the number
        // bullet 1: TODO: NaN - not sure we'd ever get this in JSON
        var pic;
        // bullet 2:
        if (value >= 0) {
            pic = variables[0];
        } else {
            pic = variables[1];
        }
        var adjustedNumber;
        // bullet 3:
        if (pic.picture.indexOf(properties.percent) !== -1) {
            adjustedNumber = value * 100;
        } else if (pic.picture.indexOf(properties['per-mille']) !== -1) {
            adjustedNumber = value * 1000;
        } else {
            adjustedNumber = value;
        }
        // bullet 4:
        // TODO: infinity - not sure we'd ever get this in JSON
        // bullet 5:
        var mantissa, exponent;
        if (pic.minimumExponentSize === 0) {
            mantissa = adjustedNumber;
        } else {
            // mantissa * 10^exponent = adjustedNumber
            var maxMantissa = Math.pow(10, pic.scalingFactor);
            var minMantissa = Math.pow(10, pic.scalingFactor - 1);
            mantissa = adjustedNumber;
            exponent = 0;
            while (mantissa < minMantissa) {
                mantissa *= 10;
                exponent -= 1;
            }
            while (mantissa > maxMantissa) {
                mantissa /= 10;
                exponent += 1;
            }
        }
        // bullet 6:
        var roundedNumber = round(mantissa, pic.maximumFactionalPartSize);
        // bullet 7:
        var makeString = function (value, dp) {
            var str = Math.abs(value).toFixed(dp);
            if (zero_digit !== '0') {
                str = str.split('').map(function (digit) {
                    if (digit >= '0' && digit <= '9') {
                        return decimalDigitFamily[digit.charCodeAt(0) - 48];
                    } else {
                        return digit;
                    }
                }).join('');
            }
            return str;
        };
        var stringValue = makeString(roundedNumber, pic.maximumFactionalPartSize);
        var decimalPos = stringValue.indexOf('.');
        if (decimalPos === -1) {
            stringValue = stringValue + decimal_separator;
        } else {
            stringValue = stringValue.replace('.', decimal_separator);
        }
        while (stringValue.charAt(0) === zero_digit) {
            stringValue = stringValue.substring(1);
        }
        while (stringValue.charAt(stringValue.length - 1) === zero_digit) {
            stringValue = stringValue.substring(0, stringValue.length - 1);
        }
        // bullets 8 & 9:
        decimalPos = stringValue.indexOf(decimal_separator);
        var padLeft = pic.minimumIntegerPartSize - decimalPos;
        var padRight = pic.minimumFactionalPartSize - (stringValue.length - decimalPos - 1);
        stringValue = (padLeft > 0 ? new Array(padLeft + 1).join(zero_digit) : '') + stringValue;
        stringValue = stringValue + (padRight > 0 ? new Array(padRight + 1).join(zero_digit) : '');
        decimalPos = stringValue.indexOf(decimal_separator);
        // bullet 10:
        if (pic.regularGrouping > 0) {
            var groupCount = Math.floor((decimalPos - 1) / pic.regularGrouping);
            for (var group = 1; group <= groupCount; group++) {
                stringValue = [stringValue.slice(0, decimalPos - group * pic.regularGrouping), grouping_separator, stringValue.slice(decimalPos - group * pic.regularGrouping)].join('');
            }
        } else {
            pic.integerPartGroupingPositions.forEach(function (pos) {
                stringValue = [stringValue.slice(0, decimalPos - pos), grouping_separator, stringValue.slice(decimalPos - pos)].join('');
                decimalPos++;
            });
        }
        // bullet 11:
        decimalPos = stringValue.indexOf(decimal_separator);
        pic.fractionalPartGroupingPositions.forEach(function (pos) {
            stringValue = [stringValue.slice(0, pos + decimalPos + 1), grouping_separator, stringValue.slice(pos + decimalPos + 1)].join('');
        });
        // bullet 12:
        decimalPos = stringValue.indexOf(decimal_separator);
        if (pic.picture.indexOf(decimal_separator) === -1 || decimalPos === stringValue.length - 1) {
            stringValue = stringValue.substring(0, stringValue.length - 1);
        }
        // bullet 13:
        if (typeof exponent !== 'undefined') {
            var stringExponent = makeString(exponent, 0);
            padLeft = pic.minimumExponentSize - stringExponent.length;
            if (padLeft > 0) {
                stringExponent = new Array(padLeft + 1).join(zero_digit) + stringExponent;
            }
            stringValue = stringValue + properties['exponent-separator'] + (exponent < 0 ? minus_sign : '') + stringExponent;
        }
        // bullet 14:
        stringValue = pic.prefix + stringValue + pic.suffix;
        return stringValue;
    }

    /**
     * Converts a number to a string using a specified number base
     * @param {number} value - the number to convert
     * @param {number} [radix] - the number base; must be between 2 and 36. Defaults to 10
     * @returns {string} - the converted string
     */
    function formatBase(value, radix) {
        // undefined inputs always return undefined
        if (typeof value === 'undefined') {
            return undefined;
        }

        value = round(value);

        if (typeof radix === 'undefined') {
            radix = 10;
        } else {
            radix = round(radix);
        }

        if (radix < 2 || radix > 36) {
            throw {
                code: 'D3100',
                stack: (new Error()).stack,
                value: radix
            };

        }

        var result = value.toString(radix);

        return result;
    }

    /**
     * Cast argument to number
     * @param {Object} arg - Argument
     * @returns {Number} numeric value of argument
     */
    function number(arg) {
        var result;

        // undefined inputs always return undefined
        if (typeof arg === 'undefined') {
            return undefined;
        }

        if (typeof arg === 'number') {
            // already a number
            result = arg;
        } else if (typeof arg === 'string' && /^-?[0-9]+(\.[0-9]+)?([Ee][-+]?[0-9]+)?$/.test(arg) && !isNaN(parseFloat(arg)) && isFinite(arg)) {
            result = parseFloat(arg);
        } else if (arg === true) {
            // boolean true casts to 1
            result = 1;
        } else if (arg === false) {
            // boolean false casts to 0
            result = 0;
        } else {
            throw {
                code: "D3030",
                value: arg,
                stack: (new Error()).stack,
                index: 1
            };
        }
        return result;
    }

    /**
     * Absolute value of a number
     * @param {Number} arg - Argument
     * @returns {Number} absolute value of argument
     */
    function abs(arg) {
        var result;

        // undefined inputs always return undefined
        if (typeof arg === 'undefined') {
            return undefined;
        }

        result = Math.abs(arg);
        return result;
    }

    /**
     * Rounds a number down to integer
     * @param {Number} arg - Argument
     * @returns {Number} rounded integer
     */
    function floor(arg) {
        var result;

        // undefined inputs always return undefined
        if (typeof arg === 'undefined') {
            return undefined;
        }

        result = Math.floor(arg);
        return result;
    }

    /**
     * Rounds a number up to integer
     * @param {Number} arg - Argument
     * @returns {Number} rounded integer
     */
    function ceil(arg) {
        var result;

        // undefined inputs always return undefined
        if (typeof arg === 'undefined') {
            return undefined;
        }

        result = Math.ceil(arg);
        return result;
    }

    /**
     * Round to half even
     * @param {Number} arg - Argument
     * @param {Number} [precision] - number of decimal places
     * @returns {Number} rounded integer
     */
    function round(arg, precision) {
        var result;

        // undefined inputs always return undefined
        if (typeof arg === 'undefined') {
            return undefined;
        }

        if (precision) {
            // shift the decimal place - this needs to be done in a string since multiplying
            // by a power of ten can introduce floating point precision errors which mess up
            // this rounding algorithm - See 'Decimal rounding' in
            // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/round
            // Shift
            var value = arg.toString().split('e');
            arg = +(value[0] + 'e' + (value[1] ? (+value[1] + precision) : precision));

        }

        // round up to nearest int
        result = Math.round(arg);
        var diff = result - arg;
        if (Math.abs(diff) === 0.5 && Math.abs(result % 2) === 1) {
            // rounded the wrong way - adjust to nearest even number
            result = result - 1;
        }
        if (precision) {
            // Shift back
            value = result.toString().split('e');
            /* istanbul ignore next */
            result = +(value[0] + 'e' + (value[1] ? (+value[1] - precision) : -precision));
        }
        if (Object.is(result, -0)) { // ESLint rule 'no-compare-neg-zero' suggests this way
            // JSON doesn't do -0
            result = 0;
        }
        return result;
    }

    /**
     * Square root of number
     * @param {Number} arg - Argument
     * @returns {Number} square root
     */
    function sqrt(arg) {
        var result;

        // undefined inputs always return undefined
        if (typeof arg === 'undefined') {
            return undefined;
        }

        if (arg < 0) {
            throw {
                stack: (new Error()).stack,
                code: "D3060",
                index: 1,
                value: arg
            };
        }

        result = Math.sqrt(arg);

        return result;
    }

    /**
     * Raises number to the power of the second number
     * @param {Number} arg - the base
     * @param {Number} exp - the exponent
     * @returns {Number} rounded integer
     */
    function power(arg, exp) {
        var result;

        // undefined inputs always return undefined
        if (typeof arg === 'undefined') {
            return undefined;
        }

        result = Math.pow(arg, exp);

        if (!isFinite(result)) {
            throw {
                stack: (new Error()).stack,
                code: "D3061",
                index: 1,
                value: arg,
                exp: exp
            };
        }

        return result;
    }

    /**
     * Returns a random number 0 <= n < 1
     * @returns {number} random number
     */
    function random() {
        return Math.random();
    }

    /**
     * Evaluate an input and return a boolean
     * @param {*} arg - Arguments
     * @returns {boolean} Boolean
     */
    function boolean(arg) {
        // cast arg to its effective boolean value
        // boolean: unchanged
        // string: zero-length -> false; otherwise -> true
        // number: 0 -> false; otherwise -> true
        // null -> false
        // array: empty -> false; length > 1 -> true
        // object: empty -> false; non-empty -> true
        // function -> false

        // undefined inputs always return undefined
        if (typeof arg === 'undefined') {
            return undefined;
        }

        var result = false;
        if (Array.isArray(arg)) {
            if (arg.length === 1) {
                result = boolean(arg[0]);
            } else if (arg.length > 1) {
                var trues = arg.filter(function (val) {
                    return boolean(val);
                });
                result = trues.length > 0;
            }
        } else if (typeof arg === 'string') {
            if (arg.length > 0) {
                result = true;
            }
        } else if (isNumeric(arg)) {
            if (arg !== 0) {
                result = true;
            }
        } else if (arg !== null && typeof arg === 'object') {
            if (Object.keys(arg).length > 0) {
                result = true;
            }
        } else if (typeof arg === 'boolean' && arg === true) {
            result = true;
        }
        return result;
    }

    /**
     * returns the Boolean NOT of the arg
     * @param {*} arg - argument
     * @returns {boolean} - NOT arg
     */
    function not(arg) {
        // undefined inputs always return undefined
        if (typeof arg === 'undefined') {
            return undefined;
        }

        return !boolean(arg);
    }

    /**
     * Helper function to build the arguments to be supplied to the function arg of the
     * HOFs map, filter, each, sift and single
     * @param {function} func - the function to be invoked
     * @param {*} arg1 - the first (required) arg - the value
     * @param {*} arg2 - the second (optional) arg - the position (index or key)
     * @param {*} arg3 - the third (optional) arg - the whole structure (array or object)
     * @returns {*[]} the argument list
     */
    function hofFuncArgs(func, arg1, arg2, arg3) {
        var func_args = [arg1]; // the first arg (the value) is required
        // the other two are optional - only supply it if the function can take it
        var length = getFunctionArity(func);
        if (length >= 2) {
            func_args.push(arg2);
        }
        if (length >= 3) {
            func_args.push(arg3);
        }
        return func_args;
    }

    /**
     * Create a map from an array of arguments
     * @param {Array} [arr] - array to map over
     * @param {Function} func - function to apply
     * @returns {Array} Map array
     */
    function* map(arr, func) {
        // undefined inputs always return undefined
        if (typeof arr === 'undefined') {
            return undefined;
        }

        var result = createSequence();
        // do the map - iterate over the arrays, and invoke func
        for (var i = 0; i < arr.length; i++) {
            var func_args = hofFuncArgs(func, arr[i], i, arr);
            // invoke func
            var res = yield* func.apply(this, func_args);
            if (typeof res !== 'undefined') {
                result.push(res);
            }
        }

        return result;
    }

    /**
     * Create a map from an array of arguments
     * @param {Array} [arr] - array to filter
     * @param {Function} func - predicate function
     * @returns {Array} Map array
     */
    function* filter(arr, func) { // eslint-disable-line require-yield
        // undefined inputs always return undefined
        if (typeof arr === 'undefined') {
            return undefined;
        }

        var result = createSequence();

        for (var i = 0; i < arr.length; i++) {
            var entry = arr[i];
            var func_args = hofFuncArgs(func, entry, i, arr);
            // invoke func
            var res = yield* func.apply(this, func_args);
            if (boolean(res)) {
                result.push(entry);
            }
        }

        return result;
    }

    /**
     * Given an array, find the single element matching a specified condition
     * Throws an exception if the number of matching elements is not exactly one
     * @param {Array} [arr] - array to filter
     * @param {Function} [func] - predicate function
     * @returns {*} Matching element
     */
    function* single(arr, func) { // eslint-disable-line require-yield
        // undefined inputs always return undefined
        if (typeof arr === 'undefined') {
            return undefined;
        }

        var hasFoundMatch = false;
        var result;

        for (var i = 0; i < arr.length; i++) {
            var entry = arr[i];
            var positiveResult = true;
            if (typeof func !== 'undefined') {
                var func_args = hofFuncArgs(func, entry, i, arr);
                // invoke func
                var res = yield* func.apply(this, func_args);
                positiveResult = boolean(res);
            }
            if (positiveResult) {
                if(!hasFoundMatch) {
                    result = entry;
                    hasFoundMatch = true;
                } else {
                    throw {
                        stack: (new Error()).stack,
                        code: "D3138",
                        index: i
                    };
                }
            }
        }

        if(!hasFoundMatch) {
            throw {
                stack: (new Error()).stack,
                code: "D3139"
            };
        }

        return result;
    }

    /**
     * Convolves (zips) each value from a set of arrays
     * @param {Array} [args] - arrays to zip
     * @returns {Array} Zipped array
     */
    function zip() {
        // this can take a variable number of arguments
        var result = [];
        var args = Array.prototype.slice.call(arguments);
        // length of the shortest array
        var length = Math.min.apply(Math, args.map(function (arg) {
            if (Array.isArray(arg)) {
                return arg.length;
            }
            return 0;
        }));
        for (var i = 0; i < length; i++) {
            var tuple = args.map((arg) => {
                return arg[i];
            });
            result.push(tuple);
        }
        return result;
    }

    /**
     * Fold left function
     * @param {Array} sequence - Sequence
     * @param {Function} func - Function
     * @param {Object} init - Initial value
     * @returns {*} Result
     */
    function* foldLeft(sequence, func, init) {
        // undefined inputs always return undefined
        if (typeof sequence === 'undefined') {
            return undefined;
        }

        var result;

        var arity = getFunctionArity(func);
        if (arity < 2) {
            throw {
                stack: (new Error()).stack,
                code: "D3050",
                index: 1
            };
        }

        var index;
        if (typeof init === 'undefined' && sequence.length > 0) {
            result = sequence[0];
            index = 1;
        } else {
            result = init;
            index = 0;
        }

        while (index < sequence.length) {
            var args = [result, sequence[index]];
            if (arity >= 3) {
                args.push(index);
            }
            if (arity >= 4) {
                args.push(sequence);
            }
            result = yield* func.apply(this, args);
            index++;
        }

        return result;
    }

    /**
     * Return keys for an object
     * @param {Object} arg - Object
     * @returns {Array} Array of keys
     */
    function keys(arg) {
        var result = createSequence();

        if (Array.isArray(arg)) {
            // merge the keys of all of the items in the array
            var merge = {};
            arg.forEach(function (item) {
                var allkeys = keys(item);
                allkeys.forEach(function (key) {
                    merge[key] = true;
                });
            });
            result = keys(merge);
        } else if (arg !== null && typeof arg === 'object' && !(isLambda(arg))) {
            Object.keys(arg).forEach(key => result.push(key));
        }
        return result;
    }

    /**
     * Return value from an object for a given key
     * @param {Object} input - Object/Array
     * @param {String} key - Key in object
     * @returns {*} Value of key in object
     */
    function lookup(input, key) {
        // lookup the 'name' item in the input
        var result;
        if (Array.isArray(input)) {
            result = createSequence();
            for(var ii = 0; ii < input.length; ii++) {
                var res =  lookup(input[ii], key);
                if (typeof res !== 'undefined') {
                    if (Array.isArray(res)) {
                        res.forEach(val => result.push(val));
                    } else {
                        result.push(res);
                    }
                }
            }
        } else if (input !== null && typeof input === 'object') {
            result = input[key];
        }
        return result;
    }

    /**
     * Append second argument to first
     * @param {Array|Object} arg1 - First argument
     * @param {Array|Object} arg2 - Second argument
     * @returns {*} Appended arguments
     */
    function append(arg1, arg2) {
        // disregard undefined args
        if (typeof arg1 === 'undefined') {
            return arg2;
        }
        if (typeof arg2 === 'undefined') {
            return arg1;
        }
        // if either argument is not an array, make it so
        if (!Array.isArray(arg1)) {
            arg1 = createSequence(arg1);
        }
        if (!Array.isArray(arg2)) {
            arg2 = [arg2];
        }
        return arg1.concat(arg2);
    }

    /**
     * Determines if the argument is undefined
     * @param {*} arg - argument
     * @returns {boolean} False if argument undefined, otherwise true
     */
    function exists(arg) {
        if (typeof arg === 'undefined') {
            return false;
        } else {
            return true;
        }
    }

    /**
     * Splits an object into an array of object with one property each
     * @param {*} arg - the object to split
     * @returns {*} - the array
     */
    function spread(arg) {
        var result = createSequence();

        if (Array.isArray(arg)) {
            // spread all of the items in the array
            arg.forEach(function (item) {
                result = append(result, spread(item));
            });
        } else if (arg !== null && typeof arg === 'object' && !isLambda(arg)) {
            for (var key in arg) {
                var obj = {};
                obj[key] = arg[key];
                result.push(obj);
            }
        } else {
            result = arg;
        }
        return result;
    }

    /**
     * Merges an array of objects into a single object.  Duplicate properties are
     * overridden by entries later in the array
     * @param {*} arg - the objects to merge
     * @returns {*} - the object
     */
    function merge(arg) {
        // undefined inputs always return undefined
        if (typeof arg === 'undefined') {
            return undefined;
        }

        var result = {};

        arg.forEach(function (obj) {
            for (var prop in obj) {
                result[prop] = obj[prop];
            }
        });
        return result;
    }

    function deepmerge(arg) {
        // undefined inputs always return undefined
        if (typeof arg === 'undefined') {
            return undefined;
        }

        // var result = {};
        
        // arg.forEach(function (obj) {
        //     for (var prop in obj) {
        //         result[prop] = deepmerge(result[prop], obj[prop]);
        //     }
        // });
        var result = deepmerger.all(arg);
        return result;
    }

    /**
     * Reverses the order of items in an array
     * @param {Array} arr - the array to reverse
     * @returns {Array} - the reversed array
     */
    function reverse(arr) {
        // undefined inputs always return undefined
        if (typeof arr === 'undefined') {
            return undefined;
        }

        if (arr.length <= 1) {
            return arr;
        }

        var length = arr.length;
        var result = new Array(length);
        for (var i = 0; i < length; i++) {
            result[length - i - 1] = arr[i];
        }

        return result;
    }

    /**
     *
     * @param {*} obj - the input object to iterate over
     * @param {*} func - the function to apply to each key/value pair
     * @returns {Array} - the resultant array
     */
    function* each(obj, func) {
        var result = createSequence();

        for (var key in obj) {
            var func_args = hofFuncArgs(func, obj[key], key, obj);
            // invoke func
            var val = yield* func.apply(this, func_args);
            if(typeof val !== 'undefined') {
                result.push(val);
            }
        }

        return result;
    }

    /**
     *
     * @param {string} [message] - the message to attach to the error
     * @throws custom error with code 'D3137'
     */
    function error(message) {
        throw {
            code: "D3137",
            stack: (new Error()).stack,
            message: message || "$error() function evaluated"
        };
    }

    /**
     *
     * @param {boolean} condition - the condition to evaluate
     * @param {string} [message] - the message to attach to the error
     * @throws custom error with code 'D3137'
     * @returns {undefined}
     */
    function assert(condition, message) {
        if(!condition) {
            throw {
                code: "D3141",
                stack: (new Error()).stack,
                message: message || "$assert() statement failed"
            };
        }

        return undefined;
    }

    /**
     *
     * @param {*} [value] - the input to which the type will be checked
     * @returns {string} - the type of the input
     */
    function type(value) {
        if (value === undefined) {
            return undefined;
        }

        if (value === null) {
            return 'null';
        }

        if (isNumeric(value)) {
            return 'number';
        }

        if (typeof value === 'string') {
            return 'string';
        }

        if (typeof value === 'boolean') {
            return 'boolean';
        }

        if(Array.isArray(value)) {
            return 'array';
        }

        if(isFunction(value)) {
            return 'function';
        }

        return 'object';
    }

    /**
     * Implements the merge sort (stable) with optional comparator function
     *
     * @param {Array} arr - the array to sort
     * @param {*} comparator - comparator function
     * @returns {Array} - sorted array
     */
    function* sort(arr, comparator) {
        // undefined inputs always return undefined
        if (typeof arr === 'undefined') {
            return undefined;
        }

        if (arr.length <= 1) {
            return arr;
        }

        var comp;
        if (typeof comparator === 'undefined') {
            // inject a default comparator - only works for numeric or string arrays
            if (!isArrayOfNumbers(arr) && !isArrayOfStrings(arr)) {
                throw {
                    stack: (new Error()).stack,
                    code: "D3070",
                    index: 1
                };
            }

            comp = function* (a, b) {  // eslint-disable-line require-yield
                return a > b;
            };
        } else {
            // for internal usage of functionSort (i.e. order-by syntax)
            comp = comparator;
        }

        var merge = function* (l, r) {
            var merge_iter = function* (result, left, right) {
                if (left.length === 0) {
                    Array.prototype.push.apply(result, right);
                } else if (right.length === 0) {
                    Array.prototype.push.apply(result, left);
                } else if (yield* comp(left[0], right[0])) { // invoke the comparator function
                    // if it returns true - swap left and right
                    result.push(right[0]);
                    yield* merge_iter(result, left, right.slice(1));
                } else {
                    // otherwise keep the same order
                    result.push(left[0]);
                    yield* merge_iter(result, left.slice(1), right);
                }
            };
            var merged = [];
            yield* merge_iter(merged, l, r);
            return merged;
        };

        var msort = function* (array) {
            if (!Array.isArray(array) || array.length <= 1) {
                return array;
            } else {
                var middle = Math.floor(array.length / 2);
                var left = array.slice(0, middle);
                var right = array.slice(middle);
                left = yield* msort(left);
                right = yield* msort(right);
                return yield* merge(left, right);
            }
        };

        var result = yield* msort(arr);

        return result;
    }

    /**
     * Randomly shuffles the contents of an array
     * @param {Array} arr - the input array
     * @returns {Array} the shuffled array
     */
    function shuffle(arr) {
        // undefined inputs always return undefined
        if (typeof arr === 'undefined') {
            return undefined;
        }

        if (arr.length <= 1) {
            return arr;
        }

        // shuffle using the 'inside-out' variant of the Fisher-Yates algorithm
        var result = new Array(arr.length);
        for (var i = 0; i < arr.length; i++) {
            var j = Math.floor(Math.random() * (i + 1)); // random integer such that 0 ≤ j ≤ i
            if (i !== j) {
                result[i] = result[j];
            }
            result[j] = arr[i];
        }

        return result;
    }

    /**
     * Returns the values that appear in a sequence, with duplicates eliminated.
     * @param {Array} arr - An array or sequence of values
     * @returns {Array} - sequence of distinct values
     */
    function distinct(arr) {
        // undefined inputs always return undefined
        if (typeof arr === 'undefined') {
            return undefined;
        }

        if(!Array.isArray(arr) || arr.length <= 1) {
            return arr;
        }

        var results = isSequence(arr) ? createSequence() : [];

        for(var ii = 0; ii < arr.length; ii++) {
            var value = arr[ii];
            // is this value already in the result sequence?
            var includes = false;
            for(var jj = 0; jj < results.length; jj++) {
                if (deepEquals(value, results[jj])) {
                    includes = true;
                    break;
                }
            }
            if(!includes) {
                results.push(value);
            }
        }
        return results;
    }

    /**
     * Applies a predicate function to each key/value pair in an object, and returns an object containing
     * only the key/value pairs that passed the predicate
     *
     * @param {object} arg - the object to be sifted
     * @param {object} func - the predicate function (lambda or native)
     * @returns {object} - sifted object
     */
    function* sift(arg, func) {
        var result = {};

        for (var item in arg) {
            var entry = arg[item];
            var func_args = hofFuncArgs(func, entry, item, arg);
            // invoke func
            var res = yield* func.apply(this, func_args);
            if (boolean(res)) {
                result[item] = entry;
            }
        }

        // empty objects should be changed to undefined
        if (Object.keys(result).length === 0) {
            result = undefined;
        }

        return result;
    }

    return {
        sum, count, max, min, average,
        string, substring, substringBefore, substringAfter, lowercase, uppercase, length, trim, pad,
        match, contains, replace, split, join,
        formatNumber, formatBase, number, floor, ceil, round, abs, sqrt, power, random,
        boolean, not,
        map, zip, filter, single, foldLeft, sift,
        keys, lookup, append, exists, spread, merge, deepmerge, reverse, each, error, assert, type, sort, shuffle, distinct,
        base64encode, base64decode,  encodeUrlComponent, encodeUrl, decodeUrlComponent, decodeUrl
    };
})();

module.exports = functions;

}).call(this)}).call(this,typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
},{"./utils":7,"deepmerge":1}],4:[function(require,module,exports){
/**
 * © Copyright IBM Corp. 2016, 2017 All Rights Reserved
 *   Project name: JSONata
 *   This project is licensed under the MIT License, see LICENSE
 */

/**
 * @module JSONata
 * @description JSON query and transformation language
 */

var datetime = require('./datetime');
var fn = require('./functions');
var utils = require('./utils');
var parser = require('./parser');
var parseSignature = require('./signature');
var deepmerge = require('deepmerge');

/**
 * jsonata
 * @function
 * @param {Object} expr - JSONata expression
 * @returns {{evaluate: evaluate, assign: assign}} Evaluated expression
 */
var jsonata = (function() {
    'use strict';

    var isNumeric = utils.isNumeric;
    var isArrayOfStrings = utils.isArrayOfStrings;
    var isArrayOfNumbers = utils.isArrayOfNumbers;
    var createSequence = utils.createSequence;
    var isSequence = utils.isSequence;
    var isFunction = utils.isFunction;
    var isLambda = utils.isLambda;
    var isIterable = utils.isIterable;
    var getFunctionArity = utils.getFunctionArity;
    var isDeepEqual = utils.isDeepEqual;

    // Start of Evaluator code

    var staticFrame = createFrame(null);

    /**
     * Evaluate expression against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function* evaluate(expr, input, environment) {
        var result;

        var entryCallback = environment.lookup('__evaluate_entry');
        if(entryCallback) {
            entryCallback(expr, input, environment);
        }

        switch (expr.type) {
            case 'path':
                result = yield * evaluatePath(expr, input, environment);
                break;
            case 'binary':
                result = yield * evaluateBinary(expr, input, environment);
                break;
            case 'unary':
                result = yield * evaluateUnary(expr, input, environment);
                break;
            case 'name':
                result = evaluateName(expr, input, environment);
                break;
            case 'string':
            case 'number':
            case 'value':
                result = evaluateLiteral(expr, input, environment);
                break;
            case 'wildcard':
                result = evaluateWildcard(expr, input, environment);
                break;
            case 'descendant':
                result = evaluateDescendants(expr, input, environment);
                break;
            case 'parent':
                result = environment.lookup(expr.slot.label);
                break;
            case 'condition':
                result = yield * evaluateCondition(expr, input, environment);
                break;
            case 'block':
                result = yield * evaluateBlock(expr, input, environment);
                break;
            case 'bind':
                result = yield * evaluateBindExpression(expr, input, environment);
                break;
            case 'regex':
                result = evaluateRegex(expr, input, environment);
                break;
            case 'function':
                result = yield * evaluateFunction(expr, input, environment);
                break;
            case 'variable':
                result = evaluateVariable(expr, input, environment);
                break;
            case 'lambda':
                result = evaluateLambda(expr, input, environment);
                break;
            case 'partial':
                result = yield * evaluatePartialApplication(expr, input, environment);
                break;
            case 'apply':
                result = yield * evaluateApplyExpression(expr, input, environment);
                break;
            case 'transform':
                result = evaluateTransformExpression(expr, input, environment);
                break;
        }

        if(environment.async &&
            (typeof result === 'undefined' || result === null || typeof result.then !== 'function')) {
            result = Promise.resolve(result);
        }
        if(environment.async && typeof result.then === 'function' && expr.nextFunction && typeof result[expr.nextFunction] === 'function') {
            // although this is a 'thenable', it is chaining a different function
            // so don't yield since yielding will trigger the .then()
        } else {
            result = yield result;
        }

        if (Object.prototype.hasOwnProperty.call(expr, 'predicate')) {
            for(var ii = 0; ii < expr.predicate.length; ii++) {
                result = yield * evaluateFilter(expr.predicate[ii].expr, result, environment);
            }
        }

        if (expr.type !== 'path' && Object.prototype.hasOwnProperty.call(expr, 'group')) {
            result = yield * evaluateGroupExpression(expr.group, result, environment);
        }

        var exitCallback = environment.lookup('__evaluate_exit');
        if(exitCallback) {
            exitCallback(expr, input, environment, result);
        }

        if(result && isSequence(result) && !result.tupleStream) {
            if(expr.keepArray) {
                result.keepSingleton = true;
            }
            if(result.length === 0) {
                result = undefined;
            } else if(result.length === 1) {
                result =  result.keepSingleton ? result : result[0];
            }

        }

        return result;
    }

    /**
     * Evaluate path expression against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function* evaluatePath(expr, input, environment) {
        var inputSequence;
        // expr is an array of steps
        // if the first step is a variable reference ($...), including root reference ($$),
        //   then the path is absolute rather than relative
        if (Array.isArray(input) && expr.steps[0].type !== 'variable') {
            inputSequence = input;
        } else {
            // if input is not an array, make it so
            inputSequence = createSequence(input);
        }

        var resultSequence;
        var isTupleStream = false;
        var tupleBindings = undefined;

        // evaluate each step in turn
        for(var ii = 0; ii < expr.steps.length; ii++) {
            var step = expr.steps[ii];

            if(step.tuple) {
                isTupleStream = true;
            }

            // if the first step is an explicit array constructor, then just evaluate that (i.e. don't iterate over a context array)
            if(ii === 0 && step.consarray) {
                resultSequence = yield * evaluate(step, inputSequence, environment);
            } else {
                if(isTupleStream) {
                    tupleBindings = yield * evaluateTupleStep(step, inputSequence, tupleBindings, environment);
                } else {
                    resultSequence = yield * evaluateStep(step, inputSequence, environment, ii === expr.steps.length - 1);
                }
            }

            if (!isTupleStream && (typeof resultSequence === 'undefined' || resultSequence.length === 0)) {
                break;
            }

            if(typeof step.focus === 'undefined') {
                inputSequence = resultSequence;
            }

        }

        if(isTupleStream) {
            if(expr.tuple) {
                // tuple stream is carrying ancestry information - keep this
                resultSequence = tupleBindings;
            } else {
                resultSequence = createSequence();
                for (ii = 0; ii < tupleBindings.length; ii++) {
                    resultSequence.push(tupleBindings[ii]['@']);
                }
            }
        }

        if(expr.keepSingletonArray) {
            if(!isSequence(resultSequence)) {
                resultSequence = createSequence(resultSequence);
            }
            resultSequence.keepSingleton = true;
        }

        if (expr.hasOwnProperty('group')) {
            resultSequence = yield* evaluateGroupExpression(expr.group, isTupleStream ? tupleBindings : resultSequence, environment)
        }

        return resultSequence;
    }

    function createFrameFromTuple(environment, tuple) {
        var frame = createFrame(environment);
        for(const prop in tuple) {
            frame.bind(prop, tuple[prop]);
        }
        return frame;
    }

    /**
     * Evaluate a step within a path
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @param {boolean} lastStep - flag the last step in a path
     * @returns {*} Evaluated input data
     */
    function* evaluateStep(expr, input, environment, lastStep) {
        var result;
        if(expr.type === 'sort') {
             result = yield* evaluateSortExpression(expr, input, environment);
             if(expr.stages) {
                 result = yield* evaluateStages(expr.stages, result, environment);
             }
             return result;
        }

        result = createSequence();

        for(var ii = 0; ii < input.length; ii++) {
            var res = yield * evaluate(expr, input[ii], environment);
            if(expr.stages) {
                for(var ss = 0; ss < expr.stages.length; ss++) {
                    res = yield* evaluateFilter(expr.stages[ss].expr, res, environment);
                }
            }
            if(typeof res !== 'undefined') {
                result.push(res);
            }
        }

        var resultSequence = createSequence();
        if(lastStep && result.length === 1 && Array.isArray(result[0]) && !isSequence(result[0])) {
            resultSequence = result[0];
        } else {
            // flatten the sequence
            result.forEach(function(res) {
                if (!Array.isArray(res) || res.cons) {
                    // it's not an array - just push into the result sequence
                    resultSequence.push(res);
                } else {
                    // res is a sequence - flatten it into the parent sequence
                    res.forEach(val => resultSequence.push(val));
                }
            });
        }

        return resultSequence;
    }

    function* evaluateStages(stages, input, environment) {
        var result = input;
        for(var ss = 0; ss < stages.length; ss++) {
            var stage = stages[ss];
            switch(stage.type) {
                case 'filter':
                    result = yield * evaluateFilter(stage.expr, result, environment);
                    break;
                case 'index':
                    for(var ee = 0; ee < result.length; ee++) {
                        var tuple = result[ee];
                        tuple[stage.value] = ee;
                    }
                    break;
            }
        }
        return result;
    }

    /**
     * Evaluate a step within a path
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} tupleBindings - The tuple stream
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function* evaluateTupleStep(expr, input, tupleBindings, environment) {
        var result;
        if(expr.type === 'sort') {
            if(tupleBindings) {
                result = yield* evaluateSortExpression(expr, tupleBindings, environment);
            } else {
                var sorted = yield* evaluateSortExpression(expr, input, environment);
                result = createSequence();
                result.tupleStream = true;
                for(var ss = 0; ss < sorted.length; ss++) {
                    var tuple = {'@': sorted[ss]};
                    tuple[expr.index] = ss;
                    result.push(tuple);
                }
            }
            if(expr.stages) {
                result = yield* evaluateStages(expr.stages, result, environment);
            }
            return result;
        }

        result = createSequence();
        result.tupleStream = true;
        var stepEnv = environment;
        if(tupleBindings === undefined) {
            tupleBindings = input.map(item => { return {'@': item} });
        }

        for(var ee = 0; ee < tupleBindings.length; ee++) {
            stepEnv = createFrameFromTuple(environment, tupleBindings[ee]);
            var res = yield* evaluate(expr, tupleBindings[ee]['@'], stepEnv);
            // res is the binding sequence for the output tuple stream
            if(typeof res !== 'undefined') {
                if (!Array.isArray(res)) {
                    res = [res];
                }
                for (var bb = 0; bb < res.length; bb++) {
                    tuple = {};
                    Object.assign(tuple, tupleBindings[ee]);
                    if(res.tupleStream) {
                        Object.assign(tuple, res[bb]);
                    } else {
                        if (expr.focus) {
                            tuple[expr.focus] = res[bb];
                            tuple['@'] = tupleBindings[ee]['@'];
                        } else {
                            tuple['@'] = res[bb];
                        }
                        if (expr.index) {
                            tuple[expr.index] = bb;
                        }
                        if (expr.ancestor) {
                            tuple[expr.ancestor.label] = tupleBindings[ee]['@'];
                        }
                    }
                    result.push(tuple);
                }
            }
        }

        if(expr.stages) {
            result = yield * evaluateStages(expr.stages, result, environment);
        }

        return result;
    }

    /**
     * Apply filter predicate to input data
     * @param {Object} predicate - filter expression
     * @param {Object} input - Input data to apply predicates against
     * @param {Object} environment - Environment
     * @returns {*} Result after applying predicates
     */
    function* evaluateFilter(predicate, input, environment) {
        var results = createSequence();
        if( input && input.tupleStream) {
            results.tupleStream = true;
        }
        if (!Array.isArray(input)) {
            input = createSequence(input);
        }
        if (predicate.type === 'number') {
            var index = Math.floor(predicate.value);  // round it down
            if (index < 0) {
                // count in from end of array
                index = input.length + index;
            }
            var item = input[index];
            if(typeof item !== 'undefined') {
                if(Array.isArray(item)) {
                    results = item;
                } else {
                    results.push(item);
                }
            }
        } else {
            for (index = 0; index < input.length; index++) {
                var item = input[index];
                var context = item;
                var env = environment;
                if(input.tupleStream) {
                    context = item['@'];
                    env = createFrameFromTuple(environment, item);
                }
                var res = yield* evaluate(predicate, context, env);
                if (isNumeric(res)) {
                    res = [res];
                }
                if (isArrayOfNumbers(res)) {
                    res.forEach(function (ires) {
                        // round it down
                        var ii = Math.floor(ires);
                        if (ii < 0) {
                            // count in from end of array
                            ii = input.length + ii;
                        }
                        if (ii === index) {
                            results.push(item);
                        }
                    });
                } else if (fn.boolean(res)) { // truthy
                    results.push(item);
                }
            }
        }
        return results;
    }

    /**
     * Evaluate binary expression against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function * evaluateBinary(expr, input, environment) {
        var result;
        var lhs = yield * evaluate(expr.lhs, input, environment);
        var rhs = yield * evaluate(expr.rhs, input, environment);
        var op = expr.value;

        try {
            switch (op) {
                case '+':
                case '-':
                case '*':
                case '/':
                case '%':
                    result = evaluateNumericExpression(lhs, rhs, op);
                    break;
                case '=':
                case '!=':
                    result = evaluateEqualityExpression(lhs, rhs, op);
                    break;
                case '<':
                case '<=':
                case '>':
                case '>=':
                    result = evaluateComparisonExpression(lhs, rhs, op);
                    break;
                case '&':
                    result = evaluateStringConcat(lhs, rhs);
                    break;
                case 'and':
                case 'or':
                    result = evaluateBooleanExpression(lhs, rhs, op);
                    break;
                case '..':
                    result = evaluateRangeExpression(lhs, rhs);
                    break;
                case 'in':
                    result = evaluateIncludesExpression(lhs, rhs);
                    break;
            }
        } catch(err) {
            err.position = expr.position;
            err.token = op;
            throw err;
        }
        return result;
    }

    /**
     * Evaluate unary expression against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function* evaluateUnary(expr, input, environment) {
        var result;

        switch (expr.value) {
            case '-':
                result = yield * evaluate(expr.expression, input, environment);
                if(typeof result === 'undefined') {
                    result = undefined;
                } else if (isNumeric(result)) {
                    result = -result;
                } else {
                    throw {
                        code: "D1002",
                        stack: (new Error()).stack,
                        position: expr.position,
                        token: expr.value,
                        value: result
                    };
                }
                break;
            case '[':
                // array constructor - evaluate each item
                result = [];
                for(var ii = 0; ii < expr.expressions.length; ii++) {
                    var item = expr.expressions[ii];
                    var value = yield * evaluate(item, input, environment);
                    if (typeof value !== 'undefined') {
                        if(item.value === '[') {
                            result.push(value);
                        } else {
                            result = fn.append(result, value);
                        }
                    }
                }
                if(expr.consarray) {
                    Object.defineProperty(result, 'cons', {
                        enumerable: false,
                        configurable: false,
                        value: true
                    });
                }
                break;
            case '{':
                // object constructor - apply grouping
                result = yield * evaluateGroupExpression(expr, input, environment);
                break;

        }
        return result;
    }

    /**
     * Evaluate name object against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function evaluateName(expr, input, environment) {
        // lookup the 'name' item in the input
        return fn.lookup(input, expr.value);
    }

    /**
     * Evaluate literal against input data
     * @param {Object} expr - JSONata expression
     * @returns {*} Evaluated input data
     */
    function evaluateLiteral(expr) {
        return expr.value;
    }

    /**
     * Evaluate wildcard against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @returns {*} Evaluated input data
     */
    function evaluateWildcard(expr, input) {
        var results = createSequence();
        if (input !== null && typeof input === 'object') {
            Object.keys(input).forEach(function (key) {
                var value = input[key];
                if(Array.isArray(value)) {
                    value = flatten(value);
                    results = fn.append(results, value);
                } else {
                    results.push(value);
                }
            });
        }

        //        result = normalizeSequence(results);
        return results;
    }

    /**
     * Returns a flattened array
     * @param {Array} arg - the array to be flatten
     * @param {Array} flattened - carries the flattened array - if not defined, will initialize to []
     * @returns {Array} - the flattened array
     */
    function flatten(arg, flattened) {
        if(typeof flattened === 'undefined') {
            flattened = [];
        }
        if(Array.isArray(arg)) {
            arg.forEach(function (item) {
                flatten(item, flattened);
            });
        } else {
            flattened.push(arg);
        }
        return flattened;
    }

    /**
     * Evaluate descendants against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @returns {*} Evaluated input data
     */
    function evaluateDescendants(expr, input) {
        var result;
        var resultSequence = createSequence();
        if (typeof input !== 'undefined') {
            // traverse all descendants of this object/array
            recurseDescendants(input, resultSequence);
            if (resultSequence.length === 1) {
                result = resultSequence[0];
            } else {
                result = resultSequence;
            }
        }
        return result;
    }

    /**
     * Recurse through descendants
     * @param {Object} input - Input data
     * @param {Object} results - Results
     */
    function recurseDescendants(input, results) {
        // this is the equivalent of //* in XPath
        if (!Array.isArray(input)) {
            results.push(input);
        }
        if (Array.isArray(input)) {
            input.forEach(function (member) {
                recurseDescendants(member, results);
            });
        } else if (input !== null && typeof input === 'object') {
            Object.keys(input).forEach(function (key) {
                recurseDescendants(input[key], results);
            });
        }
    }

    /**
     * Evaluate numeric expression against input data
     * @param {Object} lhs - LHS value
     * @param {Object} rhs - RHS value
     * @param {Object} op - opcode
     * @returns {*} Result
     */
    function evaluateNumericExpression(lhs, rhs, op) {
        var result;

        if (typeof lhs !== 'undefined' && !isNumeric(lhs)) {
            throw {
                code: "T2001",
                stack: (new Error()).stack,
                value: lhs
            };
        }
        if (typeof rhs !== 'undefined' && !isNumeric(rhs)) {
            throw {
                code: "T2002",
                stack: (new Error()).stack,
                value: rhs
            };
        }

        if (typeof lhs === 'undefined' || typeof rhs === 'undefined') {
            // if either side is undefined, the result is undefined
            return result;
        }

        switch (op) {
            case '+':
                result = lhs + rhs;
                break;
            case '-':
                result = lhs - rhs;
                break;
            case '*':
                result = lhs * rhs;
                break;
            case '/':
                result = lhs / rhs;
                break;
            case '%':
                result = lhs % rhs;
                break;
        }
        return result;
    }

    /**
     * Evaluate equality expression against input data
     * @param {Object} lhs - LHS value
     * @param {Object} rhs - RHS value
     * @param {Object} op - opcode
     * @returns {*} Result
     */
    function evaluateEqualityExpression(lhs, rhs, op) {
        var result;

        // type checks
        var ltype = typeof lhs;
        var rtype = typeof rhs;

        if (ltype === 'undefined' || rtype === 'undefined') {
            // if either side is undefined, the result is false
            return false;
        }

        switch (op) {
            case '=':
                result = isDeepEqual(lhs, rhs);
                break;
            case '!=':
                result = !isDeepEqual(lhs, rhs);
                break;
        }
        return result;
    }

    /**
     * Evaluate comparison expression against input data
     * @param {Object} lhs - LHS value
     * @param {Object} rhs - RHS value
     * @param {Object} op - opcode
     * @returns {*} Result
     */
    function evaluateComparisonExpression(lhs, rhs, op) {
        var result;

        // type checks
        var ltype = typeof lhs;
        var rtype = typeof rhs;

        var lcomparable = (ltype === 'undefined' || ltype === 'string' || ltype === 'number');
        var rcomparable = (rtype === 'undefined' || rtype === 'string' || rtype === 'number');

        // if either aa or bb are not comparable (string or numeric) values, then throw an error
        if (!lcomparable || !rcomparable) {
            throw {
                code: "T2010",
                stack: (new Error()).stack,
                value: !(ltype === 'string' || ltype === 'number') ? lhs : rhs
            };
        }

        // if either side is undefined, the result is undefined
        if (ltype === 'undefined' || rtype === 'undefined') {
            return undefined;
        }

        //if aa and bb are not of the same type
        if (ltype !== rtype) {
            throw {
                code: "T2009",
                stack: (new Error()).stack,
                value: lhs,
                value2: rhs
            };
        }

        switch (op) {
            case '<':
                result = lhs < rhs;
                break;
            case '<=':
                result = lhs <= rhs;
                break;
            case '>':
                result = lhs > rhs;
                break;
            case '>=':
                result = lhs >= rhs;
                break;
        }
        return result;
    }

    /**
     * Inclusion operator - in
     *
     * @param {Object} lhs - LHS value
     * @param {Object} rhs - RHS value
     * @returns {boolean} - true if lhs is a member of rhs
     */
    function evaluateIncludesExpression(lhs, rhs) {
        var result = false;

        if (typeof lhs === 'undefined' || typeof rhs === 'undefined') {
            // if either side is undefined, the result is false
            return false;
        }

        if(!Array.isArray(rhs)) {
            rhs = [rhs];
        }

        for(var i = 0; i < rhs.length; i++) {
            if(rhs[i] === lhs) {
                result = true;
                break;
            }
        }

        return result;
    }

    /**
     * Evaluate boolean expression against input data
     * @param {Object} lhs - LHS value
     * @param {Object} rhs - RHS value
     * @param {Object} op - opcode
     * @returns {*} Result
     */
    function evaluateBooleanExpression(lhs, rhs, op) {
        var result;

        var lBool = fn.boolean(lhs);
        var rBool = fn.boolean(rhs);

        if (typeof  lBool === 'undefined') {
            lBool = false;
        }

        if (typeof  rBool === 'undefined') {
            rBool = false;
        }

        switch (op) {
            case 'and':
                result = lBool && rBool;
                break;
            case 'or':
                result = lBool || rBool;
                break;
        }
        return result;
    }

    /**
     * Evaluate string concatenation against input data
     * @param {Object} lhs - LHS value
     * @param {Object} rhs - RHS value
     * @returns {string|*} Concatenated string
     */
    function evaluateStringConcat(lhs, rhs) {
        var result;

        var lstr = '';
        var rstr = '';
        if (typeof lhs !== 'undefined') {
            lstr = fn.string(lhs);
        }
        if (typeof rhs !== 'undefined') {
            rstr = fn.string(rhs);
        }

        result = lstr.concat(rstr);
        return result;
    }

    /**
     * Evaluate group expression against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {{}} Evaluated input data
     */
    function* evaluateGroupExpression(expr, input, environment) {
        var result = {};
        var groups = {};
        var reduce = input && input.tupleStream ? true : false;
        // group the input sequence by 'key' expression
        if (!Array.isArray(input)) {
            input = createSequence(input);
        }

        for(var itemIndex = 0; itemIndex < input.length; itemIndex++) {
            var item = input[itemIndex];
            var env = reduce ? createFrameFromTuple(environment, item) : environment;
            for(var pairIndex = 0; pairIndex < expr.lhs.length; pairIndex++) {
                var pair = expr.lhs[pairIndex];
                var key = yield * evaluate(pair[0], reduce ? item['@'] : item, env);
                // key has to be a string
                if (typeof  key !== 'string') {
                    throw {
                        code: "T1003",
                        stack: (new Error()).stack,
                        position: expr.position,
                        value: key
                    };
                }
                var entry = {data: item, exprIndex: pairIndex};
                if (groups.hasOwnProperty(key)) {
                    // a value already exists in this slot
                    if(groups[key].exprIndex !== pairIndex) {
                        // this key has been generated by another expression in this group
                        // when multiple key expressions evaluate to the same key, then error D1009 must be thrown
                        throw {
                            code: "D1009",
                            stack: (new Error()).stack,
                            position: expr.position,
                            value: key
                        };
                    }

                    // append it as an array
                    groups[key].data = fn.append(groups[key].data, item);
                } else {
                    groups[key] = entry;
                }
            }
        }

        // iterate over the groups to evaluate the 'value' expression
        for (key in groups) {
            entry = groups[key];
            var context = entry.data;
            var env = environment;
            if (reduce) {
                var tuple = reduceTupleStream(entry.data);
                context = tuple['@'];
                delete tuple['@'];
                env = createFrameFromTuple(environment, tuple);
            }
            var value = yield * evaluate(expr.lhs[entry.exprIndex][1], context, env);
            if(typeof value !== 'undefined') {
                result[key] = value;
            }
        }

        return result;
    }

    function reduceTupleStream(tupleStream) {
        if(!Array.isArray(tupleStream)) {
            return tupleStream;
        }
        var result = {};
        Object.assign(result, tupleStream[0]);
        for(var ii = 1; ii < tupleStream.length; ii++) {
            for(const prop in tupleStream[ii]) {
                result[prop] = fn.append(result[prop], tupleStream[ii][prop]);
            }
        }
        return result;
    }

    /**
     * Evaluate range expression against input data
     * @param {Object} lhs - LHS value
     * @param {Object} rhs - RHS value
     * @returns {Array} Resultant array
     */
    function evaluateRangeExpression(lhs, rhs) {
        var result;

        if (typeof lhs !== 'undefined' && !Number.isInteger(lhs)) {
            throw {
                code: "T2003",
                stack: (new Error()).stack,
                value: lhs
            };
        }
        if (typeof rhs !== 'undefined' && !Number.isInteger(rhs)) {
            throw {
                code: "T2004",
                stack: (new Error()).stack,
                value: rhs
            };
        }

        if (typeof lhs === 'undefined' || typeof rhs === 'undefined') {
            // if either side is undefined, the result is undefined
            return result;
        }

        if (lhs > rhs) {
            // if the lhs is greater than the rhs, return undefined
            return result;
        }

        // limit the size of the array to ten million entries (1e7)
        // this is an implementation defined limit to protect against
        // memory and performance issues.  This value may increase in the future.
        var size = rhs - lhs + 1;
        if(size > 1e7) {
            throw {
                code: "D2014",
                stack: (new Error()).stack,
                value: size
            };
        }

        result = new Array(size);
        for (var item = lhs, index = 0; item <= rhs; item++, index++) {
            result[index] = item;
        }
        result.sequence = true;
        return result;
    }

    /**
     * Evaluate bind expression against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function* evaluateBindExpression(expr, input, environment) {
        // The RHS is the expression to evaluate
        // The LHS is the name of the variable to bind to - should be a VARIABLE token (enforced by parser)
        var value = yield * evaluate(expr.rhs, input, environment);
        environment.bind(expr.lhs.value, value);
        return value;
    }

    /**
     * Evaluate condition against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function* evaluateCondition(expr, input, environment) {
        var result;
        var condition = yield * evaluate(expr.condition, input, environment);
        if (fn.boolean(condition)) {
            result = yield * evaluate(expr.then, input, environment);
        } else if (typeof expr.else !== 'undefined') {
            result = yield * evaluate(expr.else, input, environment);
        }
        return result;
    }

    /**
     * Evaluate block against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function* evaluateBlock(expr, input, environment) {
        var result;
        // create a new frame to limit the scope of variable assignments
        // TODO, only do this if the post-parse stage has flagged this as required
        var frame = createFrame(environment);
        // invoke each expression in turn
        // only return the result of the last one
        for(var ii = 0; ii < expr.expressions.length; ii++) {
            result = yield * evaluate(expr.expressions[ii], input, frame);
        }

        return result;
    }

    /**
     * Prepare a regex
     * @param {Object} expr - expression containing regex
     * @returns {Function} Higher order function representing prepared regex
     */
    function evaluateRegex(expr) {
        var re = new jsonata.RegexEngine(expr.value);
        var closure = function(str, fromIndex) {
            var result;
            re.lastIndex = fromIndex || 0;
            var match = re.exec(str);
            if(match !== null) {
                result = {
                    match: match[0],
                    start: match.index,
                    end: match.index + match[0].length,
                    groups: []
                };
                if(match.length > 1) {
                    for(var i = 1; i < match.length; i++) {
                        result.groups.push(match[i]);
                    }
                }
                result.next = function() {
                    if(re.lastIndex >= str.length) {
                        return undefined;
                    } else {
                        var next = closure(str, re.lastIndex);
                        if(next && next.match === '') {
                            // matches zero length string; this will never progress
                            throw {
                                code: "D1004",
                                stack: (new Error()).stack,
                                position: expr.position,
                                value: expr.value.source
                            };
                        }
                        return next;
                    }
                };
            }

            return result;
        };
        return closure;
    }

    /**
     * Evaluate variable against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function evaluateVariable(expr, input, environment) {
        // lookup the variable value in the environment
        var result;
        // if the variable name is empty string, then it refers to context value
        if (expr.value === '') {
            result = input && input.outerWrapper ? input[0] : input;
        } else {
            result = environment.lookup(expr.value);
        }
        return result;
    }

    /**
     * sort / order-by operator
     * @param {Object} expr - AST for operator
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Ordered sequence
     */
    function* evaluateSortExpression(expr, input, environment) {
        var result;

        // evaluate the lhs, then sort the results in order according to rhs expression
        //var lhs = yield * evaluate(expr.lhs, input, environment);
        var lhs = input;
        var isTupleSort = input.tupleStream ? true : false;

        // sort the lhs array
        // use comparator function
        var comparator = function*(a, b) { // eslint-disable-line require-yield
            // expr.terms is an array of order-by in priority order
            var comp = 0;
            for(var index = 0; comp === 0 && index < expr.terms.length; index++) {
                var term = expr.terms[index];
                //evaluate the sort term in the context of a
                var context = a;
                var env = environment;
                if(isTupleSort) {
                    context = a['@'];
                    env = createFrameFromTuple(environment, a);
                }
                var aa = yield * evaluate(term.expression, context, env);
                //evaluate the sort term in the context of b
                context = b;
                env = environment;
                if(isTupleSort) {
                    context = b['@'];
                    env = createFrameFromTuple(environment, b);
                }
                var bb = yield * evaluate(term.expression, context, env);

                // type checks
                var atype = typeof aa;
                var btype = typeof bb;
                // undefined should be last in sort order
                if(atype === 'undefined') {
                    // swap them, unless btype is also undefined
                    comp = (btype === 'undefined') ? 0 : 1;
                    continue;
                }
                if(btype === 'undefined') {
                    comp = -1;
                    continue;
                }

                // if aa or bb are not string or numeric values, then throw an error
                if(!(atype === 'string' || atype === 'number') || !(btype === 'string' || btype === 'number')) {
                    throw {
                        code: "T2008",
                        stack: (new Error()).stack,
                        position: expr.position,
                        value: !(atype === 'string' || atype === 'number') ? aa : bb
                    };
                }

                //if aa and bb are not of the same type
                if(atype !== btype) {
                    throw {
                        code: "T2007",
                        stack: (new Error()).stack,
                        position: expr.position,
                        value: aa,
                        value2: bb
                    };
                }
                if(aa === bb) {
                    // both the same - move on to next term
                    continue;
                } else if (aa < bb) {
                    comp = -1;
                } else {
                    comp = 1;
                }
                if(term.descending === true) {
                    comp = -comp;
                }
            }
            // only swap a & b if comp equals 1
            return comp === 1;
        };

        var focus = {
            environment: environment,
            input: input
        };
        // the `focus` is passed in as the `this` for the invoked function
        result = yield * fn.sort.apply(focus, [lhs, comparator]);

        return result;
    }

    /**
     * create a transformer function
     * @param {Object} expr - AST for operator
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} tranformer function
     */
    function evaluateTransformExpression(expr, input, environment) {
        // create a function to implement the transform definition
        var transformer = function*(obj) { // signature <(oa):o>
            // undefined inputs always return undefined
            if(typeof obj === 'undefined') {
                return undefined;
            }

            // this function returns a copy of obj with changes specified by the pattern/operation
            var cloneFunction = environment.lookup('clone');
            if(!isFunction(cloneFunction)) {
                // throw type error
                throw {
                    code: "T2013",
                    stack: (new Error()).stack,
                    position: expr.position
                };
            }
            var result = yield * apply(cloneFunction, [obj], null, environment);
            var matches = yield * evaluate(expr.pattern, result, environment);
            if(typeof matches !== 'undefined') {
                if(!Array.isArray(matches)) {
                    matches = [matches];
                }
                for(var ii = 0; ii < matches.length; ii++) {
                    var match = matches[ii];
                    // evaluate the update value for each match
                    var update = yield * evaluate(expr.update, match, environment);
                    // update must be an object
                    var updateType = typeof update;
                    if(updateType !== 'undefined') {
                        if(updateType !== 'object' || update === null || Array.isArray(update)) {
                            // throw type error
                            throw {
                                code: "T2011",
                                stack: (new Error()).stack,
                                position: expr.update.position,
                                value: update
                            };
                        }
                        // merge the update
                        // for(var prop in update) {
                        //     match[prop] = update[prop];
                        // }
                        for (var prop in update) {
                          match[prop] = deepmerge(match[prop], update[prop]);
                        }
                    }

                    // delete, if specified, must be an array of strings (or single string)
                    if(typeof expr.delete !== 'undefined') {
                        var deletions = yield * evaluate(expr.delete, match, environment);
                        if(typeof deletions !== 'undefined') {
                            var val = deletions;
                            if (!Array.isArray(deletions)) {
                                deletions = [deletions];
                            }
                            if (!isArrayOfStrings(deletions)) {
                                // throw type error
                                throw {
                                    code: "T2012",
                                    stack: (new Error()).stack,
                                    position: expr.delete.position,
                                    value: val
                                };
                            }
                            for (var jj = 0; jj < deletions.length; jj++) {
                                if(typeof match === 'object' && match !== null) {
                                    delete match[deletions[jj]];
                                }
                            }
                        }
                    }
                }
            }

            return result;
        };

        return defineFunction(transformer, '<(oa):o>');
    }

    var chainAST = parser('function($f, $g) { function($x){ $g($f($x)) } }');

    /**
     * Apply the function on the RHS using the sequence on the LHS as the first argument
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function* evaluateApplyExpression(expr, input, environment) {
        var result;


        var lhs = yield * evaluate(expr.lhs, input, environment);
        if(expr.rhs.type === 'function') {
            // this is a function _invocation_; invoke it with lhs expression as the first argument
            result = yield * evaluateFunction(expr.rhs, input, environment, { context: lhs });
        } else {
            var func = yield * evaluate(expr.rhs, input, environment);

            if(!isFunction(func)) {
                throw {
                    code: "T2006",
                    stack: (new Error()).stack,
                    position: expr.position,
                    value: func
                };
            }

            if(isFunction(lhs)) {
                // this is function chaining (func1 ~> func2)
                // λ($f, $g) { λ($x){ $g($f($x)) } }
                var chain = yield * evaluate(chainAST, null, environment);
                result = yield * apply(chain, [lhs, func], null, environment);
            } else {
                result = yield * apply(func, [lhs], null, environment);
            }

        }

        return result;
    }

    /**
     * Evaluate function against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function* evaluateFunction(expr, input, environment, applyto) {
        var result;

        // create the procedure
        // can't assume that expr.procedure is a lambda type directly
        // could be an expression that evaluates to a function (e.g. variable reference, parens expr etc.
        // evaluate it generically first, then check that it is a function.  Throw error if not.
        var proc = yield * evaluate(expr.procedure, input, environment);

        if (typeof proc === 'undefined' && expr.procedure.type === 'path' && environment.lookup(expr.procedure.steps[0].value)) {
            // help the user out here if they simply forgot the leading $
            throw {
                code: "T1005",
                stack: (new Error()).stack,
                position: expr.position,
                token: expr.procedure.steps[0].value
            };
        }

        var evaluatedArgs = [];
        if(typeof applyto !== 'undefined') {
            evaluatedArgs.push(applyto.context);
        }
        // eager evaluation - evaluate the arguments
        for (var jj = 0; jj < expr.arguments.length; jj++) {
            const arg = yield* evaluate(expr.arguments[jj], input, environment);
            if(isFunction(arg)) {
                // wrap this in a closure
                const closure = function* (...params) {
                    // invoke func
                    return yield * apply(arg, params, null, environment);
                };
                closure.arity = getFunctionArity(arg);
                evaluatedArgs.push(closure);
            } else {
                evaluatedArgs.push(arg);
            }
        }
        // apply the procedure
        var procName = expr.procedure.type === 'path' ? expr.procedure.steps[0].value : expr.procedure.value;
        try {
            if(typeof proc === 'object') {
                proc.token = procName;
                proc.position = expr.position;
            }
            result = yield * apply(proc, evaluatedArgs, input, environment);
        } catch (err) {
            if(!err.position) {
                // add the position field to the error
                err.position = expr.position;
            }
            if (!err.token) {
                // and the function identifier
                err.token = procName;
            }
            throw err;
        }
        return result;
    }

    /**
     * Apply procedure or function
     * @param {Object} proc - Procedure
     * @param {Array} args - Arguments
     * @param {Object} input - input
     * @param {Object} environment - environment
     * @returns {*} Result of procedure
     */
    function* apply(proc, args, input, environment) {
        var result;
        result = yield * applyInner(proc, args, input, environment);
        while(isLambda(result) && result.thunk === true) {
            // trampoline loop - this gets invoked as a result of tail-call optimization
            // the function returned a tail-call thunk
            // unpack it, evaluate its arguments, and apply the tail call
            var next = yield * evaluate(result.body.procedure, result.input, result.environment);
            if(result.body.procedure.type === 'variable') {
                next.token = result.body.procedure.value;
            }
            next.position = result.body.procedure.position;
            var evaluatedArgs = [];
            for(var ii = 0; ii < result.body.arguments.length; ii++) {
                evaluatedArgs.push(yield * evaluate(result.body.arguments[ii], result.input, result.environment));
            }

            result = yield * applyInner(next, evaluatedArgs, input, environment);
        }
        return result;
    }

    /**
     * Apply procedure or function
     * @param {Object} proc - Procedure
     * @param {Array} args - Arguments
     * @param {Object} input - input
     * @param {Object} environment - environment
     * @returns {*} Result of procedure
     */
    function* applyInner(proc, args, input, environment) {
        var result;
        try {
            var validatedArgs = args;
            if (proc) {
                validatedArgs = validateArguments(proc.signature, args, input);
            }

            if (isLambda(proc)) {
                result = yield* applyProcedure(proc, validatedArgs);
            } else if (proc && proc._jsonata_function === true) {
                var focus = {
                    environment: environment,
                    input: input
                };
                // the `focus` is passed in as the `this` for the invoked function
                result = proc.implementation.apply(focus, validatedArgs);
                // `proc.implementation` might be a generator function
                // and `result` might be a generator - if so, yield
                if (isIterable(result)) {
                    result = yield* result;
                }
            } else if (typeof proc === 'function') {
                // typically these are functions that are returned by the invocation of plugin functions
                // the `input` is being passed in as the `this` for the invoked function
                // this is so that functions that return objects containing functions can chain
                // e.g. $func().next().next()
                result = proc.apply(input, validatedArgs);
                /* istanbul ignore next */
                if (isIterable(result)) {
                    result = yield* result;
                }
            } else {
                throw {
                    code: "T1006",
                    stack: (new Error()).stack
                };
            }
        } catch(err) {
            if(proc) {
                if (typeof err.token == 'undefined' && typeof proc.token !== 'undefined') {
                    err.token = proc.token;
                }
                err.position = proc.position;
            }
            throw err;
        }
        return result;
    }

    /**
     * Evaluate lambda against input data
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {{lambda: boolean, input: *, environment: *, arguments: *, body: *}} Evaluated input data
     */
    function evaluateLambda(expr, input, environment) {
        // make a function (closure)
        var procedure = {
            _jsonata_lambda: true,
            input: input,
            environment: environment,
            arguments: expr.arguments,
            signature: expr.signature,
            body: expr.body
        };
        if(expr.thunk === true) {
            procedure.thunk = true;
        }
        procedure.apply = function*(self, args) {
            return yield * apply(procedure, args, input, self.environment);
        };
        return procedure;
    }

    /**
     * Evaluate partial application
     * @param {Object} expr - JSONata expression
     * @param {Object} input - Input data to evaluate against
     * @param {Object} environment - Environment
     * @returns {*} Evaluated input data
     */
    function* evaluatePartialApplication(expr, input, environment) {
        // partially apply a function
        var result;
        // evaluate the arguments
        var evaluatedArgs = [];
        for(var ii = 0; ii < expr.arguments.length; ii++) {
            var arg = expr.arguments[ii];
            if (arg.type === 'operator' && arg.value === '?') {
                evaluatedArgs.push(arg);
            } else {
                evaluatedArgs.push(yield * evaluate(arg, input, environment));
            }
        }
        // lookup the procedure
        var proc = yield * evaluate(expr.procedure, input, environment);
        if (typeof proc === 'undefined' && expr.procedure.type === 'path' && environment.lookup(expr.procedure.steps[0].value)) {
            // help the user out here if they simply forgot the leading $
            throw {
                code: "T1007",
                stack: (new Error()).stack,
                position: expr.position,
                token: expr.procedure.steps[0].value
            };
        }
        if (isLambda(proc)) {
            result = partialApplyProcedure(proc, evaluatedArgs);
        } else if (proc && proc._jsonata_function === true) {
            result = partialApplyNativeFunction(proc.implementation, evaluatedArgs);
        } else if (typeof proc === 'function') {
            result = partialApplyNativeFunction(proc, evaluatedArgs);
        } else {
            throw {
                code: "T1008",
                stack: (new Error()).stack,
                position: expr.position,
                token: expr.procedure.type === 'path' ? expr.procedure.steps[0].value : expr.procedure.value
            };
        }
        return result;
    }

    /**
     * Validate the arguments against the signature validator (if it exists)
     * @param {Function} signature - validator function
     * @param {Array} args - function arguments
     * @param {*} context - context value
     * @returns {Array} - validated arguments
     */
    function validateArguments(signature, args, context) {
        if(typeof signature === 'undefined') {
            // nothing to validate
            return args;
        }
        var validatedArgs = signature.validate(args, context);
        return validatedArgs;
    }

    /**
     * Apply procedure
     * @param {Object} proc - Procedure
     * @param {Array} args - Arguments
     * @returns {*} Result of procedure
     */
    function* applyProcedure(proc, args) {
        var result;
        var env = createFrame(proc.environment);
        proc.arguments.forEach(function (param, index) {
            env.bind(param.value, args[index]);
        });
        if (typeof proc.body === 'function') {
            // this is a lambda that wraps a native function - generated by partially evaluating a native
            result = yield * applyNativeFunction(proc.body, env);
        } else {
            result = yield * evaluate(proc.body, proc.input, env);
        }
        return result;
    }

    /**
     * Partially apply procedure
     * @param {Object} proc - Procedure
     * @param {Array} args - Arguments
     * @returns {{lambda: boolean, input: *, environment: {bind, lookup}, arguments: Array, body: *}} Result of partially applied procedure
     */
    function partialApplyProcedure(proc, args) {
        // create a closure, bind the supplied parameters and return a function that takes the remaining (?) parameters
        var env = createFrame(proc.environment);
        var unboundArgs = [];
        proc.arguments.forEach(function (param, index) {
            var arg = args[index];
            if (arg && arg.type === 'operator' && arg.value === '?') {
                unboundArgs.push(param);
            } else {
                env.bind(param.value, arg);
            }
        });
        var procedure = {
            _jsonata_lambda: true,
            input: proc.input,
            environment: env,
            arguments: unboundArgs,
            body: proc.body
        };
        return procedure;
    }

    /**
     * Partially apply native function
     * @param {Function} native - Native function
     * @param {Array} args - Arguments
     * @returns {{lambda: boolean, input: *, environment: {bind, lookup}, arguments: Array, body: *}} Result of partially applying native function
     */
    function partialApplyNativeFunction(native, args) {
        // create a lambda function that wraps and invokes the native function
        // get the list of declared arguments from the native function
        // this has to be picked out from the toString() value
        var sigArgs = getNativeFunctionArguments(native);
        sigArgs = sigArgs.map(function (sigArg) {
            return '$' + sigArg.trim();
        });
        var body = 'function(' + sigArgs.join(', ') + '){ _ }';

        var bodyAST = parser(body);
        bodyAST.body = native;

        var partial = partialApplyProcedure(bodyAST, args);
        return partial;
    }

    /**
     * Apply native function
     * @param {Object} proc - Procedure
     * @param {Object} env - Environment
     * @returns {*} Result of applying native function
     */
    function* applyNativeFunction(proc, env) {
        var sigArgs = getNativeFunctionArguments(proc);
        // generate the array of arguments for invoking the function - look them up in the environment
        var args = sigArgs.map(function (sigArg) {
            return env.lookup(sigArg.trim());
        });

        var focus = {
            environment: env
        };
        var result = proc.apply(focus, args);
        if(isIterable(result)) {
            result = yield * result;
        }
        return result;
    }

    /**
     * Get native function arguments
     * @param {Function} func - Function
     * @returns {*|Array} Native function arguments
     */
    function getNativeFunctionArguments(func) {
        var signature = func.toString();
        var sigParens = /\(([^)]*)\)/.exec(signature)[1]; // the contents of the parens
        var sigArgs = sigParens.split(',');
        return sigArgs;
    }

    /**
     * Creates a function definition
     * @param {Function} func - function implementation in Javascript
     * @param {string} signature - JSONata function signature definition
     * @returns {{implementation: *, signature: *}} function definition
     */
    function defineFunction(func, signature) {
        var definition = {
            _jsonata_function: true,
            implementation: func
        };
        if(typeof signature !== 'undefined') {
            definition.signature = parseSignature(signature);
        }
        return definition;
    }


    /**
     * parses and evaluates the supplied expression
     * @param {string} expr - expression to evaluate
     * @returns {*} - result of evaluating the expression
     */
    function* functionEval(expr, focus) {
        // undefined inputs always return undefined
        if(typeof expr === 'undefined') {
            return undefined;
        }
        var input = this.input;
        if(typeof focus !== 'undefined') {
            input = focus;
            // if the input is a JSON array, then wrap it in a singleton sequence so it gets treated as a single input
            if(Array.isArray(input) && !isSequence(input)) {
                input = createSequence(input);
                input.outerWrapper = true;
            }
        }

        try {
            var ast = parser(expr, false);
        } catch(err) {
            // error parsing the expression passed to $eval
            populateMessage(err);
            throw {
                stack: (new Error()).stack,
                code: "D3120",
                value: err.message,
                error: err
            };
        }
        try {
            var result = yield* evaluate(ast, input, this.environment);
        } catch(err) {
            // error evaluating the expression passed to $eval
            populateMessage(err);
            throw {
                stack: (new Error()).stack,
                code: "D3121",
                value:err.message,
                error: err
            };
        }

        return result;
    }

    /**
     * Clones an object
     * @param {Object} arg - object to clone (deep copy)
     * @returns {*} - the cloned object
     */
    function functionClone(arg) {
        // undefined inputs always return undefined
        if(typeof arg === 'undefined') {
            return undefined;
        }

        return JSON.parse(fn.string(arg));
    }

    /**
     * Create frame
     * @param {Object} enclosingEnvironment - Enclosing environment
     * @returns {{bind: bind, lookup: lookup}} Created frame
     */
    function createFrame(enclosingEnvironment) {
        var bindings = {};
        return {
            bind: function (name, value) {
                bindings[name] = value;
            },
            lookup: function (name) {
                var value;
                if(bindings.hasOwnProperty(name)) {
                    value = bindings[name];
                } else if (enclosingEnvironment) {
                    value = enclosingEnvironment.lookup(name);
                }
                return value;
            },
            timestamp: enclosingEnvironment ? enclosingEnvironment.timestamp : null,
            async: enclosingEnvironment ? enclosingEnvironment.async : false,
            global: enclosingEnvironment ? enclosingEnvironment.global : {
                ancestry: [ null ]
            }
        };
    }

    // Function registration
    staticFrame.bind('sum', defineFunction(fn.sum, '<a<n>:n>'));
    staticFrame.bind('count', defineFunction(fn.count, '<a:n>'));
    staticFrame.bind('max', defineFunction(fn.max, '<a<n>:n>'));
    staticFrame.bind('min', defineFunction(fn.min, '<a<n>:n>'));
    staticFrame.bind('average', defineFunction(fn.average, '<a<n>:n>'));
    staticFrame.bind('string', defineFunction(fn.string, '<x-b?:s>'));
    staticFrame.bind('substring', defineFunction(fn.substring, '<s-nn?:s>'));
    staticFrame.bind('substringBefore', defineFunction(fn.substringBefore, '<s-s:s>'));
    staticFrame.bind('substringAfter', defineFunction(fn.substringAfter, '<s-s:s>'));
    staticFrame.bind('lowercase', defineFunction(fn.lowercase, '<s-:s>'));
    staticFrame.bind('uppercase', defineFunction(fn.uppercase, '<s-:s>'));
    staticFrame.bind('length', defineFunction(fn.length, '<s-:n>'));
    staticFrame.bind('trim', defineFunction(fn.trim, '<s-:s>'));
    staticFrame.bind('pad', defineFunction(fn.pad, '<s-ns?:s>'));
    staticFrame.bind('match', defineFunction(fn.match, '<s-f<s:o>n?:a<o>>'));
    staticFrame.bind('contains', defineFunction(fn.contains, '<s-(sf):b>')); // TODO <s-(sf<s:o>):b>
    staticFrame.bind('replace', defineFunction(fn.replace, '<s-(sf)(sf)n?:s>')); // TODO <s-(sf<s:o>)(sf<o:s>)n?:s>
    staticFrame.bind('split', defineFunction(fn.split, '<s-(sf)n?:a<s>>')); // TODO <s-(sf<s:o>)n?:a<s>>
    staticFrame.bind('join', defineFunction(fn.join, '<a<s>s?:s>'));
    staticFrame.bind('formatNumber', defineFunction(fn.formatNumber, '<n-so?:s>'));
    staticFrame.bind('formatBase', defineFunction(fn.formatBase, '<n-n?:s>'));
    staticFrame.bind('formatInteger', defineFunction(datetime.formatInteger, '<n-s:s>'));
    staticFrame.bind('parseInteger', defineFunction(datetime.parseInteger, '<s-s:n>'));
    staticFrame.bind('number', defineFunction(fn.number, '<(nsb)-:n>'));
    staticFrame.bind('floor', defineFunction(fn.floor, '<n-:n>'));
    staticFrame.bind('ceil', defineFunction(fn.ceil, '<n-:n>'));
    staticFrame.bind('round', defineFunction(fn.round, '<n-n?:n>'));
    staticFrame.bind('abs', defineFunction(fn.abs, '<n-:n>'));
    staticFrame.bind('sqrt', defineFunction(fn.sqrt, '<n-:n>'));
    staticFrame.bind('power', defineFunction(fn.power, '<n-n:n>'));
    staticFrame.bind('random', defineFunction(fn.random, '<:n>'));
    staticFrame.bind('boolean', defineFunction(fn.boolean, '<x-:b>'));
    staticFrame.bind('not', defineFunction(fn.not, '<x-:b>'));
    staticFrame.bind('map', defineFunction(fn.map, '<af>'));
    staticFrame.bind('zip', defineFunction(fn.zip, '<a+>'));
    staticFrame.bind('filter', defineFunction(fn.filter, '<af>'));
    staticFrame.bind('single', defineFunction(fn.single, '<af?>'));
    staticFrame.bind('reduce', defineFunction(fn.foldLeft, '<afj?:j>')); // TODO <f<jj:j>a<j>j?:j>
    staticFrame.bind('sift', defineFunction(fn.sift, '<o-f?:o>'));
    staticFrame.bind('keys', defineFunction(fn.keys, '<x-:a<s>>'));
    staticFrame.bind('lookup', defineFunction(fn.lookup, '<x-s:x>'));
    staticFrame.bind('append', defineFunction(fn.append, '<xx:a>'));
    staticFrame.bind('exists', defineFunction(fn.exists, '<x:b>'));
    staticFrame.bind('spread', defineFunction(fn.spread, '<x-:a<o>>'));
    staticFrame.bind('merge', defineFunction(fn.merge, '<a<o>:o>'));
    staticFrame.bind('deepmerge', defineFunction(fn.deepmerge, '<a<o>:o>'));
    staticFrame.bind('reverse', defineFunction(fn.reverse, '<a:a>'));
    staticFrame.bind('each', defineFunction(fn.each, '<o-f:a>'));
    staticFrame.bind('error', defineFunction(fn.error, '<s?:x>'));
    staticFrame.bind('assert', defineFunction(fn.assert, '<bs?:x>'));
    staticFrame.bind('type', defineFunction(fn.type, '<x:s>'));
    staticFrame.bind('sort', defineFunction(fn.sort, '<af?:a>'));
    staticFrame.bind('shuffle', defineFunction(fn.shuffle, '<a:a>'));
    staticFrame.bind('distinct', defineFunction(fn.distinct, '<x:x>'));
    staticFrame.bind('base64encode', defineFunction(fn.base64encode, '<s-:s>'));
    staticFrame.bind('base64decode', defineFunction(fn.base64decode, '<s-:s>'));
    staticFrame.bind('encodeUrlComponent', defineFunction(fn.encodeUrlComponent, '<s-:s>'));
    staticFrame.bind('encodeUrl', defineFunction(fn.encodeUrl, '<s-:s>'));
    staticFrame.bind('decodeUrlComponent', defineFunction(fn.decodeUrlComponent, '<s-:s>'));
    staticFrame.bind('decodeUrl', defineFunction(fn.decodeUrl, '<s-:s>'));
    staticFrame.bind('eval', defineFunction(functionEval, '<sx?:x>'));
    staticFrame.bind('toMillis', defineFunction(datetime.toMillis, '<s-s?:n>'));
    staticFrame.bind('fromMillis', defineFunction(datetime.fromMillis, '<n-s?s?:s>'));
    staticFrame.bind('clone', defineFunction(functionClone, '<(oa)-:o>'));

    /**
     * Error codes
     *
     * Sxxxx    - Static errors (compile time)
     * Txxxx    - Type errors
     * Dxxxx    - Dynamic errors (evaluate time)
     *  01xx    - tokenizer
     *  02xx    - parser
     *  03xx    - regex parser
     *  04xx    - function signature parser/evaluator
     *  10xx    - evaluator
     *  20xx    - operators
     *  3xxx    - functions (blocks of 10 for each function)
     */
    var errorCodes = {
        "S0101": "String literal must be terminated by a matching quote",
        "S0102": "Number out of range: {{token}}",
        "S0103": "Unsupported escape sequence: \\{{token}}",
        "S0104": "The escape sequence \\u must be followed by 4 hex digits",
        "S0105": "Quoted property name must be terminated with a backquote (`)",
        "S0106": "Comment has no closing tag",
        "S0201": "Syntax error: {{token}}",
        "S0202": "Expected {{value}}, got {{token}}",
        "S0203": "Expected {{value}} before end of expression",
        "S0204": "Unknown operator: {{token}}",
        "S0205": "Unexpected token: {{token}}",
        "S0206": "Unknown expression type: {{token}}",
        "S0207": "Unexpected end of expression",
        "S0208": "Parameter {{value}} of function definition must be a variable name (start with $)",
        "S0209": "A predicate cannot follow a grouping expression in a step",
        "S0210": "Each step can only have one grouping expression",
        "S0211": "The symbol {{token}} cannot be used as a unary operator",
        "S0212": "The left side of := must be a variable name (start with $)",
        "S0213": "The literal value {{value}} cannot be used as a step within a path expression",
        "S0214": "The right side of {{token}} must be a variable name (start with $)",
        "S0215": "A context variable binding must precede any predicates on a step",
        "S0216": "A context variable binding must precede the 'order-by' clause on a step",
        "S0217": "The object representing the 'parent' cannot be derived from this expression",
        "S0301": "Empty regular expressions are not allowed",
        "S0302": "No terminating / in regular expression",
        "S0402": "Choice groups containing parameterized types are not supported",
        "S0401": "Type parameters can only be applied to functions and arrays",
        "S0500": "Attempted to evaluate an expression containing syntax error(s)",
        "T0410": "Argument {{index}} of function {{token}} does not match function signature",
        "T0411": "Context value is not a compatible type with argument {{index}} of function {{token}}",
        "T0412": "Argument {{index}} of function {{token}} must be an array of {{type}}",
        "D1001": "Number out of range: {{value}}",
        "D1002": "Cannot negate a non-numeric value: {{value}}",
        "T1003": "Key in object structure must evaluate to a string; got: {{value}}",
        "D1004": "Regular expression matches zero length string",
        "T1005": "Attempted to invoke a non-function. Did you mean ${{{token}}}?",
        "T1006": "Attempted to invoke a non-function",
        "T1007": "Attempted to partially apply a non-function. Did you mean ${{{token}}}?",
        "T1008": "Attempted to partially apply a non-function",
        "D1009": "Multiple key definitions evaluate to same key: {{value}}",
        "T1010": "The matcher function argument passed to function {{token}} does not return the correct object structure",
        "T2001": "The left side of the {{token}} operator must evaluate to a number",
        "T2002": "The right side of the {{token}} operator must evaluate to a number",
        "T2003": "The left side of the range operator (..) must evaluate to an integer",
        "T2004": "The right side of the range operator (..) must evaluate to an integer",
        "D2005": "The left side of := must be a variable name (start with $)",  // defunct - replaced by S0212 parser error
        "T2006": "The right side of the function application operator ~> must be a function",
        "T2007": "Type mismatch when comparing values {{value}} and {{value2}} in order-by clause",
        "T2008": "The expressions within an order-by clause must evaluate to numeric or string values",
        "T2009": "The values {{value}} and {{value2}} either side of operator {{token}} must be of the same data type",
        "T2010": "The expressions either side of operator {{token}} must evaluate to numeric or string values",
        "T2011": "The insert/update clause of the transform expression must evaluate to an object: {{value}}",
        "T2012": "The delete clause of the transform expression must evaluate to a string or array of strings: {{value}}",
        "T2013": "The transform expression clones the input object using the $clone() function.  This has been overridden in the current scope by a non-function.",
        "D2014": "The size of the sequence allocated by the range operator (..) must not exceed 1e6.  Attempted to allocate {{value}}.",
        "D3001": "Attempting to invoke string function on Infinity or NaN",
        "D3010": "Second argument of replace function cannot be an empty string",
        "D3011": "Fourth argument of replace function must evaluate to a positive number",
        "D3012": "Attempted to replace a matched string with a non-string value",
        "D3020": "Third argument of split function must evaluate to a positive number",
        "D3030": "Unable to cast value to a number: {{value}}",
        "D3040": "Third argument of match function must evaluate to a positive number",
        "D3050": "The second argument of reduce function must be a function with at least two arguments",
        "D3060": "The sqrt function cannot be applied to a negative number: {{value}}",
        "D3061": "The power function has resulted in a value that cannot be represented as a JSON number: base={{value}}, exponent={{exp}}",
        "D3070": "The single argument form of the sort function can only be applied to an array of strings or an array of numbers.  Use the second argument to specify a comparison function",
        "D3080": "The picture string must only contain a maximum of two sub-pictures",
        "D3081": "The sub-picture must not contain more than one instance of the 'decimal-separator' character",
        "D3082": "The sub-picture must not contain more than one instance of the 'percent' character",
        "D3083": "The sub-picture must not contain more than one instance of the 'per-mille' character",
        "D3084": "The sub-picture must not contain both a 'percent' and a 'per-mille' character",
        "D3085": "The mantissa part of a sub-picture must contain at least one character that is either an 'optional digit character' or a member of the 'decimal digit family'",
        "D3086": "The sub-picture must not contain a passive character that is preceded by an active character and that is followed by another active character",
        "D3087": "The sub-picture must not contain a 'grouping-separator' character that appears adjacent to a 'decimal-separator' character",
        "D3088": "The sub-picture must not contain a 'grouping-separator' at the end of the integer part",
        "D3089": "The sub-picture must not contain two adjacent instances of the 'grouping-separator' character",
        "D3090": "The integer part of the sub-picture must not contain a member of the 'decimal digit family' that is followed by an instance of the 'optional digit character'",
        "D3091": "The fractional part of the sub-picture must not contain an instance of the 'optional digit character' that is followed by a member of the 'decimal digit family'",
        "D3092": "A sub-picture that contains a 'percent' or 'per-mille' character must not contain a character treated as an 'exponent-separator'",
        "D3093": "The exponent part of the sub-picture must comprise only of one or more characters that are members of the 'decimal digit family'",
        "D3100": "The radix of the formatBase function must be between 2 and 36.  It was given {{value}}",
        "D3110": "The argument of the toMillis function must be an ISO 8601 formatted timestamp. Given {{value}}",
        "D3120": "Syntax error in expression passed to function eval: {{value}}",
        "D3121": "Dynamic error evaluating the expression passed to function eval: {{value}}",
        "D3130": "Formatting or parsing an integer as a sequence starting with {{value}} is not supported by this implementation",
        "D3131": "In a decimal digit pattern, all digits must be from the same decimal group",
        "D3132": "Unknown component specifier {{value}} in date/time picture string",
        "D3133": "The 'name' modifier can only be applied to months and days in the date/time picture string, not {{value}}",
        "D3134": "The timezone integer format specifier cannot have more than four digits",
        "D3135": "No matching closing bracket ']' in date/time picture string",
        "D3136": "The date/time picture string is missing specifiers required to parse the timestamp",
        "D3137": "{{{message}}}",
        "D3138": "The $single() function expected exactly 1 matching result.  Instead it matched more.",
        "D3139": "The $single() function expected exactly 1 matching result.  Instead it matched 0.",
        "D3140": "Malformed URL passed to ${{{functionName}}}(): {{value}}",
        "D3141": "{{{message}}}"
    };

    /**
     * lookup a message template from the catalog and substitute the inserts.
     * Populates `err.message` with the substituted message. Leaves `err.message`
     * untouched if code lookup fails.
     * @param {string} err - error code to lookup
     * @returns {undefined} - `err` is modified in place
     */
    function populateMessage(err) {
        var template = errorCodes[err.code];
        if(typeof template !== 'undefined') {
            // if there are any handlebars, replace them with the field references
            // triple braces - replace with value
            // double braces - replace with json stringified value
            var message = template.replace(/\{\{\{([^}]+)}}}/g, function() {
                return err[arguments[1]];
            });
            message = message.replace(/\{\{([^}]+)}}/g, function() {
                return JSON.stringify(err[arguments[1]]);
            });
            err.message = message;
        }
        // Otherwise retain the original `err.message`
    }

    /**
     * JSONata
     * @param {Object} expr - JSONata expression
     * @param {Object} options
     * @param {boolean} options.recover: attempt to recover on parse error
     * @param {Function} options.RegexEngine: RegEx class constructor to use
     * @returns {{evaluate: evaluate, assign: assign}} Evaluated expression
     */
    function jsonata(expr, options) {
        var ast;
        var errors;
        try {
            ast = parser(expr, options && options.recover);
            errors = ast.errors;
            delete ast.errors;
        } catch(err) {
            // insert error message into structure
            populateMessage(err); // possible side-effects on `err`
            throw err;
        }
        var environment = createFrame(staticFrame);

        var timestamp = new Date(); // will be overridden on each call to evalute()
        environment.bind('now', defineFunction(function(picture, timezone) {
            return datetime.fromMillis(timestamp.getTime(), picture, timezone);
        }, '<s?s?:s>'));
        environment.bind('millis', defineFunction(function() {
            return timestamp.getTime();
        }, '<:n>'));

        if(options && options.RegexEngine) {
            jsonata.RegexEngine = options.RegexEngine;
        } else {
            jsonata.RegexEngine = RegExp;
        }

        return {
            evaluate: function (input, bindings, callback) {
                // throw if the expression compiled with syntax errors
                if(typeof errors !== 'undefined') {
                    var err = {
                        code: 'S0500',
                        position: 0
                    };
                    populateMessage(err); // possible side-effects on `err`
                    throw err;
                }

                if (typeof bindings !== 'undefined') {
                    var exec_env;
                    // the variable bindings have been passed in - create a frame to hold these
                    exec_env = createFrame(environment);
                    for (var v in bindings) {
                        exec_env.bind(v, bindings[v]);
                    }
                } else {
                    exec_env = environment;
                }
                // put the input document into the environment as the root object
                exec_env.bind('$', input);

                // capture the timestamp and put it in the execution environment
                // the $now() and $millis() functions will return this value - whenever it is called
                timestamp = new Date();
                exec_env.timestamp = timestamp;

                // if the input is a JSON array, then wrap it in a singleton sequence so it gets treated as a single input
                if(Array.isArray(input) && !isSequence(input)) {
                    input = createSequence(input);
                    input.outerWrapper = true;
                }

                var result, it;
                // if a callback function is supplied, then drive the generator in a promise chain
                if(typeof callback === 'function') {
                    exec_env.async = true;
                    var catchHandler = function (err) {
                        populateMessage(err); // possible side-effects on `err`
                        callback(err, null);
                    };
                    var thenHandler = function (response) {
                        result = it.next(response);
                        if (result.done) {
                            callback(null, result.value);
                        } else {
                            result.value.then(thenHandler).catch(catchHandler);
                        }
                    };
                    it = evaluate(ast, input, exec_env);
                    result = it.next();
                    result.value.then(thenHandler).catch(catchHandler);
                } else {
                    // no callback function - drive the generator to completion synchronously
                    try {
                        it = evaluate(ast, input, exec_env);
                        result = it.next();
                        while (!result.done) {
                            result = it.next(result.value);
                        }
                        return result.value;
                    } catch (err) {
                        // insert error message into structure
                        populateMessage(err); // possible side-effects on `err`
                        throw err;
                    }
                }
            },
            assign: function (name, value) {
                environment.bind(name, value);
            },
            registerFunction: function(name, implementation, signature) {
                var func = defineFunction(implementation, signature);
                environment.bind(name, func);
            },
            ast: function() {
                return ast;
            },
            errors: function() {
                return errors;
            }
        };
    }

    jsonata.parser = parser; // TODO remove this in a future release - use ast() instead

    return jsonata;

})();

module.exports = jsonata;

},{"./datetime":2,"./functions":3,"./parser":5,"./signature":6,"./utils":7,"deepmerge":1}],5:[function(require,module,exports){
/**
 * © Copyright IBM Corp. 2016, 2018 All Rights Reserved
 *   Project name: JSONata
 *   This project is licensed under the MIT License, see LICENSE
 */

var parseSignature = require('./signature');

const parser = (() => {
    'use strict';

    var operators = {
        '.': 75,
        '[': 80,
        ']': 0,
        '{': 70,
        '}': 0,
        '(': 80,
        ')': 0,
        ',': 0,
        '@': 80,
        '#': 80,
        ';': 80,
        ':': 80,
        '?': 20,
        '+': 50,
        '-': 50,
        '*': 60,
        '/': 60,
        '%': 60,
        '|': 20,
        '=': 40,
        '<': 40,
        '>': 40,
        '^': 40,
        '**': 60,
        '..': 20,
        ':=': 10,
        '!=': 40,
        '<=': 40,
        '>=': 40,
        '~>': 40,
        'and': 30,
        'or': 25,
        'in': 40,
        '&': 50,
        '!': 0,   // not an operator, but needed as a stop character for name tokens
        '~': 0   // not an operator, but needed as a stop character for name tokens
    };

    var escapes = {  // JSON string escape sequences - see json.org
        '"': '"',
        '\\': '\\',
        '/': '/',
        'b': '\b',
        'f': '\f',
        'n': '\n',
        'r': '\r',
        't': '\t'
    };

    // Tokenizer (lexer) - invoked by the parser to return one token at a time
    var tokenizer = function (path) {
        var position = 0;
        var length = path.length;

        var create = function (type, value) {
            var obj = {type: type, value: value, position: position};
            return obj;
        };

        var scanRegex = function () {
            // the prefix '/' will have been previously scanned. Find the end of the regex.
            // search for closing '/' ignoring any that are escaped, or within brackets
            var start = position;
            var depth = 0;
            var pattern;
            var flags;
            while (position < length) {
                var currentChar = path.charAt(position);
                if (currentChar === '/' && path.charAt(position - 1) !== '\\' && depth === 0) {
                    // end of regex found
                    pattern = path.substring(start, position);
                    if (pattern === '') {
                        throw {
                            code: "S0301",
                            stack: (new Error()).stack,
                            position: position
                        };
                    }
                    position++;
                    currentChar = path.charAt(position);
                    // flags
                    start = position;
                    while (currentChar === 'i' || currentChar === 'm') {
                        position++;
                        currentChar = path.charAt(position);
                    }
                    flags = path.substring(start, position) + 'g';
                    return new RegExp(pattern, flags);
                }
                if ((currentChar === '(' || currentChar === '[' || currentChar === '{') && path.charAt(position - 1) !== '\\') {
                    depth++;
                }
                if ((currentChar === ')' || currentChar === ']' || currentChar === '}') && path.charAt(position - 1) !== '\\') {
                    depth--;
                }

                position++;
            }
            throw {
                code: "S0302",
                stack: (new Error()).stack,
                position: position
            };
        };

        var next = function (prefix) {
            if (position >= length) return null;
            var currentChar = path.charAt(position);
            // skip whitespace
            while (position < length && ' \t\n\r\v'.indexOf(currentChar) > -1) {
                position++;
                currentChar = path.charAt(position);
            }
            // skip comments
            if (currentChar === '/' && path.charAt(position + 1) === '*') {
                var commentStart = position;
                position += 2;
                currentChar = path.charAt(position);
                while (!(currentChar === '*' && path.charAt(position + 1) === '/')) {
                    currentChar = path.charAt(++position);
                    if (position >= length) {
                        // no closing tag
                        throw {
                            code: "S0106",
                            stack: (new Error()).stack,
                            position: commentStart
                        };
                    }
                }
                position += 2;
                currentChar = path.charAt(position);
                return next(prefix); // need this to swallow any following whitespace
            }
            // test for regex
            if (prefix !== true && currentChar === '/') {
                position++;
                return create('regex', scanRegex());
            }
            // handle double-char operators
            if (currentChar === '.' && path.charAt(position + 1) === '.') {
                // double-dot .. range operator
                position += 2;
                return create('operator', '..');
            }
            if (currentChar === ':' && path.charAt(position + 1) === '=') {
                // := assignment
                position += 2;
                return create('operator', ':=');
            }
            if (currentChar === '!' && path.charAt(position + 1) === '=') {
                // !=
                position += 2;
                return create('operator', '!=');
            }
            if (currentChar === '>' && path.charAt(position + 1) === '=') {
                // >=
                position += 2;
                return create('operator', '>=');
            }
            if (currentChar === '<' && path.charAt(position + 1) === '=') {
                // <=
                position += 2;
                return create('operator', '<=');
            }
            if (currentChar === '*' && path.charAt(position + 1) === '*') {
                // **  descendant wildcard
                position += 2;
                return create('operator', '**');
            }
            if (currentChar === '~' && path.charAt(position + 1) === '>') {
                // ~>  chain function
                position += 2;
                return create('operator', '~>');
            }
            // test for single char operators
            if (Object.prototype.hasOwnProperty.call(operators, currentChar)) {
                position++;
                return create('operator', currentChar);
            }
            // test for string literals
            if (currentChar === '"' || currentChar === "'") {
                var quoteType = currentChar;
                // double quoted string literal - find end of string
                position++;
                var qstr = "";
                while (position < length) {
                    currentChar = path.charAt(position);
                    if (currentChar === '\\') { // escape sequence
                        position++;
                        currentChar = path.charAt(position);
                        if (Object.prototype.hasOwnProperty.call(escapes, currentChar)) {
                            qstr += escapes[currentChar];
                        } else if (currentChar === 'u') {
                            // \u should be followed by 4 hex digits
                            var octets = path.substr(position + 1, 4);
                            if (/^[0-9a-fA-F]+$/.test(octets)) {
                                var codepoint = parseInt(octets, 16);
                                qstr += String.fromCharCode(codepoint);
                                position += 4;
                            } else {
                                throw {
                                    code: "S0104",
                                    stack: (new Error()).stack,
                                    position: position
                                };
                            }
                        } else {
                            // illegal escape sequence
                            throw {
                                code: "S0103",
                                stack: (new Error()).stack,
                                position: position,
                                token: currentChar
                            };

                        }
                    } else if (currentChar === quoteType) {
                        position++;
                        return create('string', qstr);
                    } else {
                        qstr += currentChar;
                    }
                    position++;
                }
                throw {
                    code: "S0101",
                    stack: (new Error()).stack,
                    position: position
                };
            }
            // test for numbers
            var numregex = /^-?(0|([1-9][0-9]*))(\.[0-9]+)?([Ee][-+]?[0-9]+)?/;
            var match = numregex.exec(path.substring(position));
            if (match !== null) {
                var num = parseFloat(match[0]);
                if (!isNaN(num) && isFinite(num)) {
                    position += match[0].length;
                    return create('number', num);
                } else {
                    throw {
                        code: "S0102",
                        stack: (new Error()).stack,
                        position: position,
                        token: match[0]
                    };
                }
            }
            // test for quoted names (backticks)
            var name;
            if (currentChar === '`') {
                // scan for closing quote
                position++;
                var end = path.indexOf('`', position);
                if (end !== -1) {
                    name = path.substring(position, end);
                    position = end + 1;
                    return create('name', name);
                }
                position = length;
                throw {
                    code: "S0105",
                    stack: (new Error()).stack,
                    position: position
                };
            }
            // test for names
            var i = position;
            var ch;
            for (; ;) {
                ch = path.charAt(i);
                if (i === length || ' \t\n\r\v'.indexOf(ch) > -1 || Object.prototype.hasOwnProperty.call(operators, ch)) {
                    if (path.charAt(position) === '$') {
                        // variable reference
                        name = path.substring(position + 1, i);
                        position = i;
                        return create('variable', name);
                    } else {
                        name = path.substring(position, i);
                        position = i;
                        switch (name) {
                            case 'or':
                            case 'in':
                            case 'and':
                                return create('operator', name);
                            case 'true':
                                return create('value', true);
                            case 'false':
                                return create('value', false);
                            case 'null':
                                return create('value', null);
                            default:
                                if (position === length && name === '') {
                                    // whitespace at end of input
                                    return null;
                                }
                                return create('name', name);
                        }
                    }
                } else {
                    i++;
                }
            }
        };

        return next;
    };

    // This parser implements the 'Top down operator precedence' algorithm developed by Vaughan R Pratt; http://dl.acm.org/citation.cfm?id=512931.
    // and builds on the Javascript framework described by Douglas Crockford at http://javascript.crockford.com/tdop/tdop.html
    // and in 'Beautiful Code', edited by Andy Oram and Greg Wilson, Copyright 2007 O'Reilly Media, Inc. 798-0-596-51004-6

    var parser = function (source, recover) {
        var node;
        var lexer;

        var symbol_table = {};
        var errors = [];

        var remainingTokens = function () {
            var remaining = [];
            if (node.id !== '(end)') {
                remaining.push({type: node.type, value: node.value, position: node.position});
            }
            var nxt = lexer();
            while (nxt !== null) {
                remaining.push(nxt);
                nxt = lexer();
            }
            return remaining;
        };

        var base_symbol = {
            nud: function () {
                // error - symbol has been invoked as a unary operator
                var err = {
                    code: 'S0211',
                    token: this.value,
                    position: this.position
                };

                if (recover) {
                    err.remaining = remainingTokens();
                    err.type = 'error';
                    errors.push(err);
                    return err;
                } else {
                    err.stack = (new Error()).stack;
                    throw err;
                }
            }
        };

        var symbol = function (id, bp) {
            var s = symbol_table[id];
            bp = bp || 0;
            if (s) {
                if (bp >= s.lbp) {
                    s.lbp = bp;
                }
            } else {
                s = Object.create(base_symbol);
                s.id = s.value = id;
                s.lbp = bp;
                symbol_table[id] = s;
            }
            return s;
        };

        var handleError = function (err) {
            if (recover) {
                // tokenize the rest of the buffer and add it to an error token
                err.remaining = remainingTokens();
                errors.push(err);
                var symbol = symbol_table["(error)"];
                node = Object.create(symbol);
                node.error = err;
                node.type = "(error)";
                return node;
            } else {
                err.stack = (new Error()).stack;
                throw err;
            }
        };

        var advance = function (id, infix) {
            if (id && node.id !== id) {
                var code;
                if (node.id === '(end)') {
                    // unexpected end of buffer
                    code = "S0203";
                } else {
                    code = "S0202";
                }
                var err = {
                    code: code,
                    position: node.position,
                    token: node.value,
                    value: id
                };
                return handleError(err);
            }
            var next_token = lexer(infix);
            if (next_token === null) {
                node = symbol_table["(end)"];
                node.position = source.length;
                return node;
            }
            var value = next_token.value;
            var type = next_token.type;
            var symbol;
            switch (type) {
                case 'name':
                case 'variable':
                    symbol = symbol_table["(name)"];
                    break;
                case 'operator':
                    symbol = symbol_table[value];
                    if (!symbol) {
                        return handleError({
                            code: "S0204",
                            stack: (new Error()).stack,
                            position: next_token.position,
                            token: value
                        });
                    }
                    break;
                case 'string':
                case 'number':
                case 'value':
                    symbol = symbol_table["(literal)"];
                    break;
                case 'regex':
                    type = "regex";
                    symbol = symbol_table["(regex)"];
                    break;
                /* istanbul ignore next */
                default:
                    return handleError({
                        code: "S0205",
                        stack: (new Error()).stack,
                        position: next_token.position,
                        token: value
                    });
            }

            node = Object.create(symbol);
            node.value = value;
            node.type = type;
            node.position = next_token.position;
            return node;
        };

        // Pratt's algorithm
        var expression = function (rbp) {
            var left;
            var t = node;
            advance(null, true);
            left = t.nud();
            while (rbp < node.lbp) {
                t = node;
                advance();
                left = t.led(left);
            }
            return left;
        };

        var terminal = function (id) {
            var s = symbol(id, 0);
            s.nud = function () {
                return this;
            };
        };

        // match infix operators
        // <expression> <operator> <expression>
        // left associative
        var infix = function (id, bp, led) {
            var bindingPower = bp || operators[id];
            var s = symbol(id, bindingPower);
            s.led = led || function (left) {
                this.lhs = left;
                this.rhs = expression(bindingPower);
                this.type = "binary";
                return this;
            };
            return s;
        };

        // match infix operators
        // <expression> <operator> <expression>
        // right associative
        var infixr = function (id, bp, led) {
            var s = symbol(id, bp);
            s.led = led;
            return s;
        };

        // match prefix operators
        // <operator> <expression>
        var prefix = function (id, nud) {
            var s = symbol(id);
            s.nud = nud || function () {
                this.expression = expression(70);
                this.type = "unary";
                return this;
            };
            return s;
        };

        terminal("(end)");
        terminal("(name)");
        terminal("(literal)");
        terminal("(regex)");
        symbol(":");
        symbol(";");
        symbol(",");
        symbol(")");
        symbol("]");
        symbol("}");
        symbol(".."); // range operator
        infix("."); // map operator
        infix("+"); // numeric addition
        infix("-"); // numeric subtraction
        infix("*"); // numeric multiplication
        infix("/"); // numeric division
        infix("%"); // numeric modulus
        infix("="); // equality
        infix("<"); // less than
        infix(">"); // greater than
        infix("!="); // not equal to
        infix("<="); // less than or equal
        infix(">="); // greater than or equal
        infix("&"); // string concatenation
        infix("and"); // Boolean AND
        infix("or"); // Boolean OR
        infix("in"); // is member of array
        terminal("and"); // the 'keywords' can also be used as terminals (field names)
        terminal("or"); //
        terminal("in"); //
        prefix("-"); // unary numeric negation
        infix("~>"); // function application

        infixr("(error)", 10, function (left) {
            this.lhs = left;

            this.error = node.error;
            this.remaining = remainingTokens();
            this.type = 'error';
            return this;
        });

        // field wildcard (single level)
        prefix('*', function () {
            this.type = "wildcard";
            return this;
        });

        // descendant wildcard (multi-level)
        prefix('**', function () {
            this.type = "descendant";
            return this;
        });

        // parent operator
        prefix('%', function () {
            this.type = "parent";
            return this;
        });

        // function invocation
        infix("(", operators['('], function (left) {
            // left is is what we are trying to invoke
            this.procedure = left;
            this.type = 'function';
            this.arguments = [];
            if (node.id !== ')') {
                for (; ;) {
                    if (node.type === 'operator' && node.id === '?') {
                        // partial function application
                        this.type = 'partial';
                        this.arguments.push(node);
                        advance('?');
                    } else {
                        this.arguments.push(expression(0));
                    }
                    if (node.id !== ',') break;
                    advance(',');
                }
            }
            advance(")", true);
            // if the name of the function is 'function' or λ, then this is function definition (lambda function)
            if (left.type === 'name' && (left.value === 'function' || left.value === '\u03BB')) {
                // all of the args must be VARIABLE tokens
                this.arguments.forEach(function (arg, index) {
                    if (arg.type !== 'variable') {
                        return handleError({
                            code: "S0208",
                            stack: (new Error()).stack,
                            position: arg.position,
                            token: arg.value,
                            value: index + 1
                        });
                    }
                });
                this.type = 'lambda';
                // is the next token a '<' - if so, parse the function signature
                if (node.id === '<') {
                    var sigPos = node.position;
                    var depth = 1;
                    var sig = '<';
                    while (depth > 0 && node.id !== '{' && node.id !== '(end)') {
                        var tok = advance();
                        if (tok.id === '>') {
                            depth--;
                        } else if (tok.id === '<') {
                            depth++;
                        }
                        sig += tok.value;
                    }
                    advance('>');
                    try {
                        this.signature = parseSignature(sig);
                    } catch (err) {
                        // insert the position into this error
                        err.position = sigPos + err.offset;
                        return handleError(err);
                    }
                }
                // parse the function body
                advance('{');
                this.body = expression(0);
                advance('}');
            }
            return this;
        });

        // parenthesis - block expression
        prefix("(", function () {
            var expressions = [];
            while (node.id !== ")") {
                expressions.push(expression(0));
                if (node.id !== ";") {
                    break;
                }
                advance(";");
            }
            advance(")", true);
            this.type = 'block';
            this.expressions = expressions;
            return this;
        });

        // array constructor
        prefix("[", function () {
            var a = [];
            if (node.id !== "]") {
                for (; ;) {
                    var item = expression(0);
                    if (node.id === "..") {
                        // range operator
                        var range = {type: "binary", value: "..", position: node.position, lhs: item};
                        advance("..");
                        range.rhs = expression(0);
                        item = range;
                    }
                    a.push(item);
                    if (node.id !== ",") {
                        break;
                    }
                    advance(",");
                }
            }
            advance("]", true);
            this.expressions = a;
            this.type = "unary";
            return this;
        });

        // filter - predicate or array index
        infix("[", operators['['], function (left) {
            if (node.id === "]") {
                // empty predicate means maintain singleton arrays in the output
                var step = left;
                while (step && step.type === 'binary' && step.value === '[') {
                    step = step.lhs;
                }
                step.keepArray = true;
                advance("]");
                return left;
            } else {
                this.lhs = left;
                this.rhs = expression(operators[']']);
                this.type = 'binary';
                advance("]", true);
                return this;
            }
        });

        // order-by
        infix("^", operators['^'], function (left) {
            advance("(");
            var terms = [];
            for (; ;) {
                var term = {
                    descending: false
                };
                if (node.id === "<") {
                    // ascending sort
                    advance("<");
                } else if (node.id === ">") {
                    // descending sort
                    term.descending = true;
                    advance(">");
                } else {
                    //unspecified - default to ascending
                }
                term.expression = expression(0);
                terms.push(term);
                if (node.id !== ",") {
                    break;
                }
                advance(",");
            }
            advance(")");
            this.lhs = left;
            this.rhs = terms;
            this.type = 'binary';
            return this;
        });

        var objectParser = function (left) {
            var a = [];
            if (node.id !== "}") {
                for (; ;) {
                    var n = expression(0);
                    advance(":");
                    var v = expression(0);
                    a.push([n, v]); // holds an array of name/value expression pairs
                    if (node.id !== ",") {
                        break;
                    }
                    advance(",");
                }
            }
            advance("}", true);
            if (typeof left === 'undefined') {
                // NUD - unary prefix form
                this.lhs = a;
                this.type = "unary";
            } else {
                // LED - binary infix form
                this.lhs = left;
                this.rhs = a;
                this.type = 'binary';
            }
            return this;
        };

        // object constructor
        prefix("{", objectParser);

        // object grouping
        infix("{", operators['{'], objectParser);

        // bind variable
        infixr(":=", operators[':='], function (left) {
            if (left.type !== 'variable') {
                return handleError({
                    code: "S0212",
                    stack: (new Error()).stack,
                    position: left.position,
                    token: left.value
                });
            }
            this.lhs = left;
            this.rhs = expression(operators[':='] - 1); // subtract 1 from bindingPower for right associative operators
            this.type = "binary";
            return this;
        });

        // focus variable bind
        infix("@", operators['@'], function (left) {
            this.lhs = left;
            this.rhs = expression(operators['@']);
            if(this.rhs.type !== 'variable') {
                return handleError({
                    code: "S0214",
                    stack: (new Error()).stack,
                    position: this.rhs.position,
                    token: "@"
                });
            }
            this.type = "binary";
            return this;
        });

        // index (position) variable bind
        infix("#", operators['#'], function (left) {
            this.lhs = left;
            this.rhs = expression(operators['#']);
            if(this.rhs.type !== 'variable') {
                return handleError({
                    code: "S0214",
                    stack: (new Error()).stack,
                    position: this.rhs.position,
                    token: "#"
                });
            }
            this.type = "binary";
            return this;
        });

        // if/then/else ternary operator ?:
        infix("?", operators['?'], function (left) {
            this.type = 'condition';
            this.condition = left;
            this.then = expression(0);
            if (node.id === ':') {
                // else condition
                advance(":");
                this.else = expression(0);
            }
            return this;
        });

        // object transformer
        prefix("|", function () {
            this.type = 'transform';
            this.pattern = expression(0);
            advance('|');
            this.update = expression(0);
            if (node.id === ',') {
                advance(',');
                this.delete = expression(0);
            }
            advance('|');
            return this;
        });

        // tail call optimization
        // this is invoked by the post parser to analyse lambda functions to see
        // if they make a tail call.  If so, it is replaced by a thunk which will
        // be invoked by the trampoline loop during function application.
        // This enables tail-recursive functions to be written without growing the stack
        var tailCallOptimize = function (expr) {
            var result;
            if (expr.type === 'function' && !expr.predicate) {
                var thunk = {type: 'lambda', thunk: true, arguments: [], position: expr.position};
                thunk.body = expr;
                result = thunk;
            } else if (expr.type === 'condition') {
                // analyse both branches
                expr.then = tailCallOptimize(expr.then);
                if (typeof expr.else !== 'undefined') {
                    expr.else = tailCallOptimize(expr.else);
                }
                result = expr;
            } else if (expr.type === 'block') {
                // only the last expression in the block
                var length = expr.expressions.length;
                if (length > 0) {
                    expr.expressions[length - 1] = tailCallOptimize(expr.expressions[length - 1]);
                }
                result = expr;
            } else {
                result = expr;
            }
            return result;
        };

        var ancestorLabel = 0;
        var ancestorIndex = 0;
        var ancestry = [];

        var seekParent = function (node, slot) {
            switch (node.type) {
                case 'name':
                case 'wildcard':
                    slot.level--;
                    if(slot.level === 0) {
                        if (typeof node.ancestor === 'undefined') {
                            node.ancestor = slot;
                        } else {
                            // reuse the existing label
                            ancestry[slot.index].slot.label = node.ancestor.label;
                            node.ancestor = slot;
                        }
                        node.tuple = true;
                    }
                    break;
                case 'parent':
                    slot.level++;
                    break;
                case 'block':
                    // look in last expression in the block
                    if(node.expressions.length > 0) {
                        node.tuple = true;
                        slot = seekParent(node.expressions[node.expressions.length - 1], slot);
                    }
                    break;
                case 'path':
                    // last step in path
                    node.tuple = true;
                    var index = node.steps.length - 1;
                    slot = seekParent(node.steps[index--], slot);
                    while (slot.level > 0 && index >= 0) {
                        // check previous steps
                        slot = seekParent(node.steps[index--], slot);
                    }
                    break;
                default:
                    // error - can't derive ancestor
                    throw {
                        code: "S0217",
                        token: node.type,
                        position: node.position
                    };
            }
            return slot;
        };

        var pushAncestry = function(result, value) {
            if(typeof value.seekingParent !== 'undefined' || value.type === 'parent') {
                var slots = (typeof value.seekingParent !== 'undefined') ? value.seekingParent : [];
                if (value.type === 'parent') {
                    slots.push(value.slot);
                }
                if(typeof result.seekingParent === 'undefined') {
                    result.seekingParent = slots;
                } else {
                    Array.prototype.push.apply(result.seekingParent, slots);
                }
            }
        };

        var resolveAncestry = function(path) {
            var index = path.steps.length - 1;
            var laststep = path.steps[index];
            var slots = (typeof laststep.seekingParent !== 'undefined') ? laststep.seekingParent : [];
            if (laststep.type === 'parent') {
                slots.push(laststep.slot);
            }
            for(var is = 0; is < slots.length; is++) {
                var slot = slots[is];
                index = path.steps.length - 2;
                while (slot.level > 0) {
                    if (index < 0) {
                        if(typeof path.seekingParent === 'undefined') {
                            path.seekingParent = [slot];
                        } else {
                            path.seekingParent.push(slot);
                        }
                        break;
                    }
                    // try previous step
                    var step = path.steps[index--];
                    // multiple contiguous steps that bind the focus should be skipped
                    while(index >= 0 && step.focus && path.steps[index].focus) {
                        step = path.steps[index--];
                    }
                    slot = seekParent(step, slot);
                }
            }
        };

        // post-parse stage
        // the purpose of this is to add as much semantic value to the parse tree as possible
        // in order to simplify the work of the evaluator.
        // This includes flattening the parts of the AST representing location paths,
        // converting them to arrays of steps which in turn may contain arrays of predicates.
        // following this, nodes containing '.' and '[' should be eliminated from the AST.
        var processAST = function (expr) {
            var result;
            switch (expr.type) {
                case 'binary':
                    switch (expr.value) {
                        case '.':
                            var lstep = processAST(expr.lhs);

                            if (lstep.type === 'path') {
                                result = lstep;
                            } else {
                                result = {type: 'path', steps: [lstep]};
                            }
                            if(lstep.type === 'parent') {
                                result.seekingParent = [lstep.slot];
                            }
                            var rest = processAST(expr.rhs);
                            if (rest.type === 'function' &&
                                rest.procedure.type === 'path' &&
                                rest.procedure.steps.length === 1 &&
                                rest.procedure.steps[0].type === 'name' &&
                                result.steps[result.steps.length - 1].type === 'function') {
                                // next function in chain of functions - will override a thenable
                                result.steps[result.steps.length - 1].nextFunction = rest.procedure.steps[0].value;
                            }
                            if (rest.type === 'path') {
                                Array.prototype.push.apply(result.steps, rest.steps);
                            } else {
                                if(typeof rest.predicate !== 'undefined') {
                                    rest.stages = rest.predicate;
                                    delete rest.predicate;
                                }
                                result.steps.push(rest);
                            }
                            // any steps within a path that are string literals, should be changed to 'name'
                            result.steps.filter(function (step) {
                                if (step.type === 'number' || step.type === 'value') {
                                    // don't allow steps to be numbers or the values true/false/null
                                    throw {
                                        code: "S0213",
                                        stack: (new Error()).stack,
                                        position: step.position,
                                        value: step.value
                                    };
                                }
                                return step.type === 'string';
                            }).forEach(function (lit) {
                                lit.type = 'name';
                            });
                            // any step that signals keeping a singleton array, should be flagged on the path
                            if (result.steps.filter(function (step) {
                                return step.keepArray === true;
                            }).length > 0) {
                                result.keepSingletonArray = true;
                            }
                            // if first step is a path constructor, flag it for special handling
                            var firststep = result.steps[0];
                            if (firststep.type === 'unary' && firststep.value === '[') {
                                firststep.consarray = true;
                            }
                            // if the last step is an array constructor, flag it so it doesn't flatten
                            var laststep = result.steps[result.steps.length - 1];
                            if (laststep.type === 'unary' && laststep.value === '[') {
                                laststep.consarray = true;
                            }
                            resolveAncestry(result);
                            break;
                        case '[':
                            // predicated step
                            // LHS is a step or a predicated step
                            // RHS is the predicate expr
                            result = processAST(expr.lhs);
                            var step = result;
                            var type = 'predicate';
                            if (result.type === 'path') {
                                step = result.steps[result.steps.length - 1];
                                type = 'stages';
                            }
                            if (typeof step.group !== 'undefined') {
                                throw {
                                    code: "S0209",
                                    stack: (new Error()).stack,
                                    position: expr.position
                                };
                            }
                            if (typeof step[type] === 'undefined') {
                                step[type] = [];
                            }
                            var predicate = processAST(expr.rhs);
                            if(typeof predicate.seekingParent !== 'undefined') {
                                predicate.seekingParent.forEach(slot => {
                                    if(slot.level === 1) {
                                        seekParent(step, slot);
                                    } else {
                                        slot.level--;
                                    }
                                });
                                pushAncestry(step, predicate);
                            }
                            step[type].push({type: 'filter', expr: predicate, position: expr.position});
                            break;
                        case '{':
                            // group-by
                            // LHS is a step or a predicated step
                            // RHS is the object constructor expr
                            result = processAST(expr.lhs);
                            if (typeof result.group !== 'undefined') {
                                throw {
                                    code: "S0210",
                                    stack: (new Error()).stack,
                                    position: expr.position
                                };
                            }
                            // object constructor - process each pair
                            result.group = {
                                lhs: expr.rhs.map(function (pair) {
                                    return [processAST(pair[0]), processAST(pair[1])];
                                }),
                                position: expr.position
                            };
                            break;
                        case '^':
                            // order-by
                            // LHS is the array to be ordered
                            // RHS defines the terms
                            result = processAST(expr.lhs);
                            if (result.type !== 'path') {
                                result = {type: 'path', steps: [result]};
                            }
                            var sortStep = {type: 'sort', position: expr.position};
                            sortStep.terms = expr.rhs.map(function (terms) {
                                var expression = processAST(terms.expression);
                                pushAncestry(sortStep, expression);
                                return {
                                    descending: terms.descending,
                                    expression: expression
                                };
                            });
                            result.steps.push(sortStep);
                            resolveAncestry(result);
                            break;
                        case ':=':
                            result = {type: 'bind', value: expr.value, position: expr.position};
                            result.lhs = processAST(expr.lhs);
                            result.rhs = processAST(expr.rhs);
                            pushAncestry(result, result.rhs);
                            break;
                        case '@':
                            result = processAST(expr.lhs);
                            step = result;
                            if (result.type === 'path') {
                                step = result.steps[result.steps.length - 1];
                            }
                            // throw error if there are any predicates defined at this point
                            // at this point the only type of stages can be predicates
                            if(typeof step.stages !== 'undefined' || typeof step.predicate !== 'undefined') {
                                throw {
                                    code: "S0215",
                                    stack: (new Error()).stack,
                                    position: expr.position
                                };
                            }
                            // also throw if this is applied after an 'order-by' clause
                            if(step.type === 'sort') {
                                throw {
                                    code: "S0216",
                                    stack: (new Error()).stack,
                                    position: expr.position
                                };
                            }
                            if(expr.keepArray) {
                                step.keepArray = true;
                            }
                            step.focus = expr.rhs.value;
                            step.tuple = true;
                            break;
                        case '#':
                            result = processAST(expr.lhs);
                            step = result;
                            if (result.type === 'path') {
                                step = result.steps[result.steps.length - 1];
                            } else {
                                result = {type: 'path', steps: [result]};
                                if (typeof step.predicate !== 'undefined') {
                                    step.stages = step.predicate;
                                    delete step.predicate;
                                }
                            }
                            if (typeof step.stages === 'undefined') {
                                step.index = expr.rhs.value;
                            } else {
                                step.stages.push({type: 'index', value: expr.rhs.value, position: expr.position});
                            }
                            step.tuple = true;
                            break;
                        case '~>':
                            result = {type: 'apply', value: expr.value, position: expr.position};
                            result.lhs = processAST(expr.lhs);
                            result.rhs = processAST(expr.rhs);
                            break;
                        default:
                            result = {type: expr.type, value: expr.value, position: expr.position};
                            result.lhs = processAST(expr.lhs);
                            result.rhs = processAST(expr.rhs);
                            pushAncestry(result, result.lhs);
                            pushAncestry(result, result.rhs);
                    }
                    break;
                case 'unary':
                    result = {type: expr.type, value: expr.value, position: expr.position};
                    if (expr.value === '[') {
                        // array constructor - process each item
                        result.expressions = expr.expressions.map(function (item) {
                            var value = processAST(item);
                            pushAncestry(result, value);
                            return value;
                        });
                    } else if (expr.value === '{') {
                        // object constructor - process each pair
                        result.lhs = expr.lhs.map(function (pair) {
                            var key = processAST(pair[0]);
                            pushAncestry(result, key);
                            var value = processAST(pair[1]);
                            pushAncestry(result, value);
                            return [key, value];
                        });
                    } else {
                        // all other unary expressions - just process the expression
                        result.expression = processAST(expr.expression);
                        // if unary minus on a number, then pre-process
                        if (expr.value === '-' && result.expression.type === 'number') {
                            result = result.expression;
                            result.value = -result.value;
                        } else {
                            pushAncestry(result, result.expression);
                        }
                    }
                    break;
                case 'function':
                case 'partial':
                    result = {type: expr.type, name: expr.name, value: expr.value, position: expr.position};
                    result.arguments = expr.arguments.map(function (arg) {
                        var argAST = processAST(arg);
                        pushAncestry(result, argAST);
                        return argAST;
                    });
                    result.procedure = processAST(expr.procedure);
                    break;
                case 'lambda':
                    result = {
                        type: expr.type,
                        arguments: expr.arguments,
                        signature: expr.signature,
                        position: expr.position
                    };
                    var body = processAST(expr.body);
                    result.body = tailCallOptimize(body);
                    break;
                case 'condition':
                    result = {type: expr.type, position: expr.position};
                    result.condition = processAST(expr.condition);
                    pushAncestry(result, result.condition);
                    result.then = processAST(expr.then);
                    pushAncestry(result, result.then);
                    if (typeof expr.else !== 'undefined') {
                        result.else = processAST(expr.else);
                        pushAncestry(result, result.else);
                    }
                    break;
                case 'transform':
                    result = {type: expr.type, position: expr.position};
                    result.pattern = processAST(expr.pattern);
                    result.update = processAST(expr.update);
                    if (typeof expr.delete !== 'undefined') {
                        result.delete = processAST(expr.delete);
                    }
                    break;
                case 'block':
                    result = {type: expr.type, position: expr.position};
                    // array of expressions - process each one
                    result.expressions = expr.expressions.map(function (item) {
                        var part = processAST(item);
                        pushAncestry(result, part);
                        if (part.consarray || (part.type === 'path' && part.steps[0].consarray)) {
                            result.consarray = true;
                        }
                        return part;
                    });
                    // TODO scan the array of expressions to see if any of them assign variables
                    // if so, need to mark the block as one that needs to create a new frame
                    break;
                case 'name':
                    result = {type: 'path', steps: [expr]};
                    if (expr.keepArray) {
                        result.keepSingletonArray = true;
                    }
                    break;
                case 'parent':
                    result = {type: 'parent', slot: { label: '!' + ancestorLabel++, level: 1, index: ancestorIndex++ } };
                    ancestry.push(result);
                    break;
                case 'string':
                case 'number':
                case 'value':
                case 'wildcard':
                case 'descendant':
                case 'variable':
                case 'regex':
                    result = expr;
                    break;
                case 'operator':
                    // the tokens 'and' and 'or' might have been used as a name rather than an operator
                    if (expr.value === 'and' || expr.value === 'or' || expr.value === 'in') {
                        expr.type = 'name';
                        result = processAST(expr);
                    } else /* istanbul ignore else */ if (expr.value === '?') {
                        // partial application
                        result = expr;
                    } else {
                        throw {
                            code: "S0201",
                            stack: (new Error()).stack,
                            position: expr.position,
                            token: expr.value
                        };
                    }
                    break;
                case 'error':
                    result = expr;
                    if (expr.lhs) {
                        result = processAST(expr.lhs);
                    }
                    break;
                default:
                    var code = "S0206";
                    /* istanbul ignore else */
                    if (expr.id === '(end)') {
                        code = "S0207";
                    }
                    var err = {
                        code: code,
                        position: expr.position,
                        token: expr.value
                    };
                    if (recover) {
                        errors.push(err);
                        return {type: 'error', error: err};
                    } else {
                        err.stack = (new Error()).stack;
                        throw err;
                    }
            }
            if (expr.keepArray) {
                result.keepArray = true;
            }
            return result;
        };

        // now invoke the tokenizer and the parser and return the syntax tree
        lexer = tokenizer(source);
        advance();
        // parse the tokens
        var expr = expression(0);
        if (node.id !== '(end)') {
            var err = {
                code: "S0201",
                position: node.position,
                token: node.value
            };
            handleError(err);
        }
        expr = processAST(expr);

        if(expr.type === 'parent' || typeof expr.seekingParent !== 'undefined') {
            // error - trying to derive ancestor at top level
            throw {
                code: "S0217",
                token: expr.type,
                position: expr.position
            };
        }

        if (errors.length > 0) {
            expr.errors = errors;
        }

        return expr;
    };

    return parser;
})();

module.exports = parser;

},{"./signature":6}],6:[function(require,module,exports){
/**
 * © Copyright IBM Corp. 2016, 2018 All Rights Reserved
 *   Project name: JSONata
 *   This project is licensed under the MIT License, see LICENSE
 */

var utils = require('./utils');

const signature = (() => {
    'use strict';

    // A mapping between the function signature symbols and the full plural of the type
    // Expected to be used in error messages
    var arraySignatureMapping = {
        "a": "arrays",
        "b": "booleans",
        "f": "functions",
        "n": "numbers",
        "o": "objects",
        "s": "strings"
    };

    /**
     * Parses a function signature definition and returns a validation function
     * @param {string} signature - the signature between the <angle brackets>
     * @returns {Function} validation function
     */
    function parseSignature(signature) {
        // create a Regex that represents this signature and return a function that when invoked,
        // returns the validated (possibly fixed-up) arguments, or throws a validation error
        // step through the signature, one symbol at a time
        var position = 1;
        var params = [];
        var param = {};
        var prevParam = param;
        while (position < signature.length) {
            var symbol = signature.charAt(position);
            if (symbol === ':') {
                // TODO figure out what to do with the return type
                // ignore it for now
                break;
            }

            var next = function () {
                params.push(param);
                prevParam = param;
                param = {};
            };

            var findClosingBracket = function (str, start, openSymbol, closeSymbol) {
                // returns the position of the closing symbol (e.g. bracket) in a string
                // that balances the opening symbol at position start
                var depth = 1;
                var position = start;
                while (position < str.length) {
                    position++;
                    symbol = str.charAt(position);
                    if (symbol === closeSymbol) {
                        depth--;
                        if (depth === 0) {
                            // we're done
                            break; // out of while loop
                        }
                    } else if (symbol === openSymbol) {
                        depth++;
                    }
                }
                return position;
            };

            switch (symbol) {
                case 's': // string
                case 'n': // number
                case 'b': // boolean
                case 'l': // not so sure about expecting null?
                case 'o': // object
                    param.regex = '[' + symbol + 'm]';
                    param.type = symbol;
                    next();
                    break;
                case 'a': // array
                    //  normally treat any value as singleton array
                    param.regex = '[asnblfom]';
                    param.type = symbol;
                    param.array = true;
                    next();
                    break;
                case 'f': // function
                    param.regex = 'f';
                    param.type = symbol;
                    next();
                    break;
                case 'j': // any JSON type
                    param.regex = '[asnblom]';
                    param.type = symbol;
                    next();
                    break;
                case 'x': // any type
                    param.regex = '[asnblfom]';
                    param.type = symbol;
                    next();
                    break;
                case '-': // use context if param not supplied
                    prevParam.context = true;
                    prevParam.contextRegex = new RegExp(prevParam.regex); // pre-compiled to test the context type at runtime
                    prevParam.regex += '?';
                    break;
                case '?': // optional param
                case '+': // one or more
                    prevParam.regex += symbol;
                    break;
                case '(': // choice of types
                    // search forward for matching ')'
                    var endParen = findClosingBracket(signature, position, '(', ')');
                    var choice = signature.substring(position + 1, endParen);
                    if (choice.indexOf('<') === -1) {
                        // no parameterized types, simple regex
                        param.regex = '[' + choice + 'm]';
                    } else {
                        // TODO harder
                        throw {
                            code: "S0402",
                            stack: (new Error()).stack,
                            value: choice,
                            offset: position
                        };
                    }
                    param.type = '(' + choice + ')';
                    position = endParen;
                    next();
                    break;
                case '<': // type parameter - can only be applied to 'a' and 'f'
                    if (prevParam.type === 'a' || prevParam.type === 'f') {
                        // search forward for matching '>'
                        var endPos = findClosingBracket(signature, position, '<', '>');
                        prevParam.subtype = signature.substring(position + 1, endPos);
                        position = endPos;
                    } else {
                        throw {
                            code: "S0401",
                            stack: (new Error()).stack,
                            value: prevParam.type,
                            offset: position
                        };
                    }
                    break;
            }
            position++;
        }
        var regexStr = '^' +
            params.map(function (param) {
                return '(' + param.regex + ')';
            }).join('') +
            '$';
        var regex = new RegExp(regexStr);
        var getSymbol = function (value) {
            var symbol;
            if (utils.isFunction(value)) {
                symbol = 'f';
            } else {
                var type = typeof value;
                switch (type) {
                    case 'string':
                        symbol = 's';
                        break;
                    case 'number':
                        symbol = 'n';
                        break;
                    case 'boolean':
                        symbol = 'b';
                        break;
                    case 'object':
                        if (value === null) {
                            symbol = 'l';
                        } else if (Array.isArray(value)) {
                            symbol = 'a';
                        } else {
                            symbol = 'o';
                        }
                        break;
                    case 'undefined':
                    default:
                        // any value can be undefined, but should be allowed to match
                        symbol = 'm'; // m for missing
                }
            }
            return symbol;
        };

        var throwValidationError = function (badArgs, badSig) {
            // to figure out where this went wrong we need apply each component of the
            // regex to each argument until we get to the one that fails to match
            var partialPattern = '^';
            var goodTo = 0;
            for (var index = 0; index < params.length; index++) {
                partialPattern += params[index].regex;
                var match = badSig.match(partialPattern);
                if (match === null) {
                    // failed here
                    throw {
                        code: "T0410",
                        stack: (new Error()).stack,
                        value: badArgs[goodTo],
                        index: goodTo + 1
                    };
                }
                goodTo = match[0].length;
            }
            // if it got this far, it's probably because of extraneous arguments (we
            // haven't added the trailing '$' in the regex yet.
            throw {
                code: "T0410",
                stack: (new Error()).stack,
                value: badArgs[goodTo],
                index: goodTo + 1
            };
        };

        return {
            definition: signature,
            validate: function (args, context) {
                var suppliedSig = '';
                args.forEach(function (arg) {
                    suppliedSig += getSymbol(arg);
                });
                var isValid = regex.exec(suppliedSig);
                if (isValid) {
                    var validatedArgs = [];
                    var argIndex = 0;
                    params.forEach(function (param, index) {
                        var arg = args[argIndex];
                        var match = isValid[index + 1];
                        if (match === '') {
                            if (param.context && param.contextRegex) {
                                // substitute context value for missing arg
                                // first check that the context value is the right type
                                var contextType = getSymbol(context);
                                // test contextType against the regex for this arg (without the trailing ?)
                                if (param.contextRegex.test(contextType)) {
                                    validatedArgs.push(context);
                                } else {
                                    // context value not compatible with this argument
                                    throw {
                                        code: "T0411",
                                        stack: (new Error()).stack,
                                        value: context,
                                        index: argIndex + 1
                                    };
                                }
                            } else {
                                validatedArgs.push(arg);
                                argIndex++;
                            }
                        } else {
                            // may have matched multiple args (if the regex ends with a '+'
                            // split into single tokens
                            match.split('').forEach(function (single) {
                                if (param.type === 'a') {
                                    if (single === 'm') {
                                        // missing (undefined)
                                        arg = undefined;
                                    } else {
                                        arg = args[argIndex];
                                        var arrayOK = true;
                                        // is there type information on the contents of the array?
                                        if (typeof param.subtype !== 'undefined') {
                                            if (single !== 'a' && match !== param.subtype) {
                                                arrayOK = false;
                                            } else if (single === 'a') {
                                                if (arg.length > 0) {
                                                    var itemType = getSymbol(arg[0]);
                                                    if (itemType !== param.subtype.charAt(0)) { // TODO recurse further
                                                        arrayOK = false;
                                                    } else {
                                                        // make sure every item in the array is this type
                                                        var differentItems = arg.filter(function (val) {
                                                            return (getSymbol(val) !== itemType);
                                                        });
                                                        arrayOK = (differentItems.length === 0);
                                                    }
                                                }
                                            }
                                        }
                                        if (!arrayOK) {
                                            throw {
                                                code: "T0412",
                                                stack: (new Error()).stack,
                                                value: arg,
                                                index: argIndex + 1,
                                                type: arraySignatureMapping[param.subtype]
                                            };
                                        }
                                        // the function expects an array. If it's not one, make it so
                                        if (single !== 'a') {
                                            arg = [arg];
                                        }
                                    }
                                    validatedArgs.push(arg);
                                    argIndex++;
                                } else {
                                    validatedArgs.push(arg);
                                    argIndex++;
                                }
                            });
                        }
                    });
                    return validatedArgs;
                }
                throwValidationError(args, suppliedSig);
            }
        };
    }

    return parseSignature;
})();

module.exports = signature;

},{"./utils":7}],7:[function(require,module,exports){
/**
 * © Copyright IBM Corp. 2016, 2018 All Rights Reserved
 *   Project name: JSONata
 *   This project is licensed under the MIT License, see LICENSE
 */

const utils = (() => {
    'use strict';

    /**
     * Check if value is a finite number
     * @param {float} n - number to evaluate
     * @returns {boolean} True if n is a finite number
     */
    function isNumeric(n) {
        var isNum = false;
        if(typeof n === 'number') {
            isNum = !isNaN(n);
            if (isNum && !isFinite(n)) {
                throw {
                    code: "D1001",
                    value: n,
                    stack: (new Error()).stack
                };
            }
        }
        return isNum;
    }

    /**
     * Returns true if the arg is an array of strings
     * @param {*} arg - the item to test
     * @returns {boolean} True if arg is an array of strings
     */
    function isArrayOfStrings(arg) {
        var result = false;
        /* istanbul ignore else */
        if(Array.isArray(arg)) {
            result = (arg.filter(function(item){return typeof item !== 'string';}).length === 0);
        }
        return result;
    }

    /**
     * Returns true if the arg is an array of numbers
     * @param {*} arg - the item to test
     * @returns {boolean} True if arg is an array of numbers
     */
    function isArrayOfNumbers(arg) {
        var result = false;
        if(Array.isArray(arg)) {
            result = (arg.filter(function(item){return !isNumeric(item);}).length === 0);
        }
        return result;
    }

    /**
     * Create an empty sequence to contain query results
     * @returns {Array} - empty sequence
     */
    function createSequence() {
        var sequence = [];
        sequence.sequence = true;
        if (arguments.length === 1) {
            sequence.push(arguments[0]);
        }
        return sequence;
    }

    /**
     * Tests if a value is a sequence
     * @param {*} value the value to test
     * @returns {boolean} true if it's a sequence
     */
    function isSequence(value) {
        return value.sequence === true && Array.isArray(value);
    }

    /**
     *
     * @param {Object} arg - expression to test
     * @returns {boolean} - true if it is a function (lambda or built-in)
     */
    function isFunction(arg) {
        return ((arg && (arg._jsonata_function === true || arg._jsonata_lambda === true)) || typeof arg === 'function');
    }

    /**
     * Returns the arity (number of arguments) of the function
     * @param {*} func - the function
     * @returns {*} - the arity
     */
    function getFunctionArity(func) {
        var arity = typeof func.arity === 'number' ? func.arity :
            typeof func.implementation === 'function' ? func.implementation.length :
                typeof func.length === 'number' ? func.length : func.arguments.length;
        return arity;
    }

    /**
     * Tests whether arg is a lambda function
     * @param {*} arg - the value to test
     * @returns {boolean} - true if it is a lambda function
     */
    function isLambda(arg) {
        return arg && arg._jsonata_lambda === true;
    }

    // istanbul ignore next
    var $Symbol = typeof Symbol === "function" ? Symbol : {};
    // istanbul ignore next
    var iteratorSymbol = $Symbol.iterator || "@@iterator";

    /**
     * @param {Object} arg - expression to test
     * @returns {boolean} - true if it is iterable
     */
    function isIterable(arg) {
        return (
            typeof arg === 'object' &&
            arg !== null &&
            iteratorSymbol in arg &&
            'next' in arg &&
            typeof arg.next === 'function'
        );
    }

    /**
     * Compares two values for equality
     * @param {*} lhs first value
     * @param {*} rhs second value
     * @returns {boolean} true if they are deep equal
     */
    function isDeepEqual(lhs, rhs) {
        if (lhs === rhs) {
            return true;
        }
        if(typeof lhs === 'object' && typeof rhs === 'object' && lhs !== null && rhs !== null) {
            if(Array.isArray(lhs) && Array.isArray(rhs)) {
                // both arrays (or sequences)
                // must be the same length
                if(lhs.length !== rhs.length) {
                    return false;
                }
                // must contain same values in same order
                for(var ii = 0; ii < lhs.length; ii++) {
                    if(!isDeepEqual(lhs[ii], rhs[ii])) {
                        return false;
                    }
                }
                return true;
            }
            // both objects
            // must have the same set of keys (in any order)
            var lkeys = Object.getOwnPropertyNames(lhs);
            var rkeys = Object.getOwnPropertyNames(rhs);
            if(lkeys.length !== rkeys.length) {
                return false;
            }
            lkeys = lkeys.sort();
            rkeys = rkeys.sort();
            for(ii=0; ii < lkeys.length; ii++) {
                if(lkeys[ii] !== rkeys[ii]) {
                    return false;
                }
            }
            // must have the same values
            for(ii=0; ii < lkeys.length; ii++) {
                var key = lkeys[ii];
                if(!isDeepEqual(lhs[key], rhs[key])) {
                    return false;
                }
            }
            return true;
        }
        return false;
    }

    /**
     * converts a string to an array of characters
     * @param {string} str - the input string
     * @returns {Array} - the array of characters
     */
    function stringToArray(str) {
        var arr = [];
        for (let char of str) {
            arr.push(char);
        }
        return arr;
    }

    return {
        isNumeric,
        isArrayOfStrings,
        isArrayOfNumbers,
        createSequence,
        isSequence,
        isFunction,
        isLambda,
        isIterable,
        getFunctionArity,
        isDeepEqual,
        stringToArray
    };
})();

module.exports = utils;

},{}]},{},[4])(4)
});