arithmetic-expression-parser

arithmetic-expression-parser is a simple arithmetic expression parser written in Kotlin. It supports the following operations:

unary: -
binary: +, -, *, /, ^ (power), % (modulo)
functions: abs, acos, asin, atan, cos, cosh, exp, ln, log, sin, sinh, sqrt, tan, tanh

For trigonometric functions, both radians and degrees are supported.

Design

The parser is build using combinators. Parsing is a two-step process:

the tokens package provides various token parsers that match certain tokens, e.g. char literals, identifiers, numbers etc.
arithmetic package defines expression parsers that use the token parsers to create parsers for arithmetic expressions.

The Expression object parses arithmetic expressions:

Expression("3 + 4")

This will return an abstract syntax tree. The tryEval extension method can be used to evaluate the expression:

Expression("3 + 4").tryEval()

The result will be Success(7.0). If an invalid expression like Expression("foo(0)") is evaluated, a Failure will be returned.

The default trigonometric unit is radians, but degrees are also supported:

val ctx = Context.Empty.copy(trigonometricUnit = TrigonometricUnit.Degree)
Expression("sin(90)").tryEval(ctx)

The result will be Success(1.0).

Global variables can be defined using upper case letters:

val ctx = Context(TrigonometricUnit.Rad, mapOf(Pair("A", 2.0)))
Expression("A + 3").tryEval(ctx)

The result will be Success(5.0).

Apache-2.0 License