gitpicard / jcalc

A simple AST based parser and interpreter for expressions. Complete project with docs and unit tests.

About

jcalc is a simple Java package that allows Java programs to parse and evaluate math expressions. It support custom variables and functions meaning that you can provide data to the expressions that are evaluated.

Usage

The full auto-generated docs are hosted here. The quickest way to get up and running is to use the JCalculator class. Call the eval method to run an expression and get the result. If you want more control or want to change the behavior of an operator, you can implement the ASTVisitor class and write your own behavior. The parser will generate an abstract syntax tree (AST) and JCalculator implements a visitor to evaluate that tree. With ASTVisitor, you can implement your own evaluation environment.

Example

Here is a short example that includes a custom variable and a custom function. Note, the function does not do any error checking but it should throw EvalException if it is passed bad arguments.

JCalculator calc = new JCalculator();
calc.setVariable("x", 15.7);
calc.setFunction("add", (args) -> args[0] + args[1]);
return calc.eval("5 * add(10, x) ^ 2");