ExpressionsEval

Evaluate expressions with your custom config. Originally made for Tensai VFX engine.

Using ExpressionsEval

<!-- pom.xml -->
<dependency>
    <groupId>dev.phomc</groupId>
    <artifactId>expressions-eval</artifactId>
    <version>0.0.1-SNAPSHOT</versi
</dependency>

Expression expr = Expression.parse("(1 + 2 * 3 + 4) / 5");
expr.eval(new SimpleEvalContext() {}, null); // The expected result is 2 in integer type

Expression expr2 = Expression.parse("x * 1.2");
expr.eval(new SimpleEvalContext() {}, VariablesInterface.of(Map.of("x", 123.456)));

Using virtual machine to call eval() repeatedly

If you are willing to call eval() multiple times, it is a good idea to compile it to virtual machine code with Expression.compile() or VirtualMachineExpression.compile() and use eval() on it:

Expression expr = Expression.compile("x * 1.2");

// ...
expr.eval(evalContext, variables);

Custom evaluate context

You can create your own evaluate context to accepts custom types and provide global variables to all expressions:

public class MyEvalContext implements SimpleEvalContext {
    @Override
    public Object applyOperator(Object a, Operator op, Object b) {
        if (a instanceof Vector3 va && b instanceof Vector3 vb) {
            return switch (op) {
            case ADD -> va.add(vb);
            case SUBTRACT -> va.sub(vb);
            case MULTIPLY -> va.mul(vb);
            case DIVIDE -> va.div(vb);
            default -> null;
            };
        }

        return super.applyOperator();
    }
}