In this project, a Scala parser combinator library is implemented and used for a JSON parser and a command line calculator. This parser combinator library can be extended to many arbitrary parsers.
- Liheng Gong
- Weiqiang Li
Our parser combinator is able to accept a String input and parse
from this input using the parser specified by user. With error
reporting mechanism, our parser combinator will let user to specify, label and
tag error messages when there is any error.
Using our library, a JSON parser is implemented to support parsing
of a JSON String input. See here for a description of the
JSON syntax. Our JSON parser will converts the JSON String input into an abstract
syntax tree representing the specified data. Similarly, our JSON parser
will report error when the input String is not considered as a valid
JSON input.
Our parser combinator and JSON parser are both well-documented with extensive unit tests.
A simple command line calculator is implemented using our parser combinator,
which parses arithmetic
expressions over floating point numbers and evaluates them. The
calculator is implemented as a Parser[Double] that
evaluates the expression on-the-fly during parsing.
This command line calculator can be run in sbt shell. Type run Calculator directly
in sbt shell will start the calculator that accepts the input from user, and calculate
the result on-the-fly. In this mode, type quit, q or exit to terminate
the calculator program.
Type run Calculator <expression> directly in sbt shell
will start the calculator and evaluates the <expression> user specified
in command line input, and directly give the result.