Expression Parser

Simple expression parser library for unity

Quick Sample

// create context
var context = new ExpresionContext<float>();

// register some variables
context.RegisterVariable("a", () => 1);
context.RegisterVariable("b", () => 2);
context.RegisterVariable("c", () => 3);

var input = "a >= b AND NOT(b) OR (a + b) >= c";

// compile expression
var compiledExpr = FloatExpressionParser.Instance.Compile(input, context, true);

// execute expression
var result = compiledExpr.Invoke();

Create your own ExpressionParser implementation to support other data types

Language Overview

Constants

Input	Value
TRUE	1
FALSE	0

Numbers

Input	Value
123	123.0
123.0	123.0
123.4	123.4

Operators

Name	Sample	Precedence
Unary Minus	-2	0
Power	2 ^ 3	1 (!!!, -2^2 = (-2) ^ 2 = 4)
Multiply	2 * 3	2
Divide	6 / 3	2
Module	5 % 3	2
Addition	2 + 3	3
Subtraction	3 - 2	3
Less Than	2 < 3	4
Less Than Or Equal	2 <= 3	4
Greater Than	2 > 3	4
Greater Than Or Equal	2 >= 3	4
Equality	2 = 3	5
Inequality	2 != 3	5
Logical and	2 > 1 AND 3 > 2	6
Logical or	2 = 3 OR 2 != 4	6

Variables

Creation of custom variables is supported. Variable name must starts with english letter or underscore. The rest of the variable name may also contains digits.

Functions

Name	Sample	Description
NOT	NOT(TRUE)	Returns FALSE if argument is true, otherwise TRUE
IF	IF(n < 5, 5, n < 25, 25, 50)	Returns the second argument if the first argument is true, returns the fourth argument if the third argument is true, and so on. Otherwise, returns the last argument. Odd number of arguments required
MIN	MIN(0, 1, ...)	Returns smallest argument
MAX	MAX(0, 1, ...)	Returns largest argument
ROUND	ROUND(1.1)	Rounds a number
CEILING	CEILING(1.1)	Round number up
FLOOR	FLOOR(1.1)	Rounds number down
LOG	LOG(8, 2)	Returns the logarithm to base B of number A

How to Install

Minimal Unity Version is 2020.1.

Library distributed as git package (How to install package from git URL)
Git URL: https://github.com/codewriter-packages/Expression-Parser.git

License

Expression-Parser is MIT licensed.