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About

Decimal data type support, for COBOL-like fixed-point operations on currency/money values.

Author: Piotr Likus

Created: 03/01/2011

Modified: 23/09/2018

Licence: BSD

Version: 1.16

This data type is designed to perform calculation with on-fly roundings & to support correct compare function (floating-point compare is unreliable).

Values are stored internally using 64-bit integer, so maximum number of digits is 18.

Precision is user-defined, so you can use this data type for currency rates.

To store decimal in file you can use "unbiased" functions or use stream i/o.

Examples

Example usage:

#include "decimal.h"

using namespace dec;
using namespace std;

// the following declares currency variable with 2 decimal points
// initialized with integer value (can be also floating-point)
decimal<2> value(143125);

// displays: Value #1 is: 143125.00
cout << "Value #1 is: " << value << endl;

// declare precise value with digits after decimal point
decimal<2> b("0.11");

// perform calculations as with any other numeric type
value += b;

// displays: Value #2 is: 143125.11
cout << "Value #2 is: " << value << endl;

// automatic rounding performed here
value /= 1000;

// displays: Value #3 is: 143.13
cout << "Value #3 is: " << value << endl;

// integer multiplication and division can be used directly in expression
// displays: Value: 143.13 * 2 is: 286.26
cout << "Value: " << value << " * 2 is: " << (value * 2) << endl;

// to use non-integer constants in expressions you need to use decimal_cast
value = value * decimal_cast<2>("3.33") / decimal_cast<2>(333.0);

// displays: Value #4 is: 1.43
cout << "Value #4 is: " << value << endl;

// to mix decimals with different precision use decimal_cast
// it will round result automatically
decimal<6> exchangeRate(12.1234);
value = decimal_cast<2>(decimal_cast<6>(value) * exchangeRate);

// displays: Value #5 is: 17.34
cout << "Value #5 is: " << value << endl;

// supports optional strong typing, e.g.
// depending on configuration mixing precision can be forbidden 
// or handled automatically
decimal<2> d2("12.03");
decimal<4> d4("123.0103");

d2 += d4; // this will fail to compile if you define DEC_TYPE_LEVEL < 2
d4 += d2; // this will fail to compile if you define DEC_TYPE_LEVEL == 0

Supported rounding modes:

  • def_round_policy: default rounding (arithmetic)
  • null_round_policy: round towards zero = truncate
  • half_down_round_policy: round half towards negative infinity
  • half_up_round_policy: round half towards positive infinity
  • half_even_round_policy: bankers' rounding, convergent rounding, statistician's rounding, Dutch rounding, Gaussian rounding
  • ceiling_round_policy: round towards positive infinity
  • floor_round_policy: round towards negative infinity
  • round_down_round_policy: round towards zero = truncate
  • round_up_round_policy: round away from zero

In order to use one of these rounding modes you need to declare your decimal variable like this:

dec::decimal<2, half_even_round_policy> a;

and it will perform required rounding automatically - for example during assignment or arithmetic operations.

Other information

For more examples please see \test directory.

Directory structure:

\doc     - documentation (licence etc.)
\include - headers
\test    - unit tests, Boost-based

Code documentation can be generated using Doxygen: http://www.doxygen.org/

Tested compilers:

  • VS2015 Community
  • VS2013 Community Update 4
  • Code::Blocks 13.12 + MinGW + gcc 4.8.4

Uses C++11 by default, define DEC_NO_CPP11 symbol if your compiler does not support this standard. To use custom namespace, define DEC_NAMESPACE symbol which should contain your target namespace for decimal type. For full list of configuration options see "Config section" in decimal.h file.

For list of project contributors, currently open issues or latest version see project site: https://github.com/vpiotr/decimal_for_cpp