Expression Parser - Evaluate Mathematical Expressions With Unity

Making games require a lot of balancing and math calculations. Sometimes you want to save a function into remote config and change it on the fly for flexible and easier testing.

I recently found out that Unity could do this. A small but helpful utility enables you to parse and evaluate mathematical expressions:

ExpressionParser https://wiki.unity3d.com/index.php/ExpressionParser

var parser = new ExpressionParser();
Expression exp = parser.EvaluateExpression("(5+3)*8^2-5*(-2)");
Debug.Log("Result: " + exp.Value);  // prints: "Result: 522"

More than that, it could also turn your expression into a delegate and inject your custom function too. I found that quite amazing.

var sinFunc = exp2.ToDelegate("x");
Debug.Log("sin(90°): " + sinFunc(90)); // prints "sin(90°): 1" 

parser.AddFunc("test", (p) => {
    Debug.Log("TEST: " + p.Length);
    return 42;
Debug.Log("Result: "+parser.Evaluate("2*test(1,5)")); /

Combine with a node-js server, we could use MathJs https://mathjs.org

let scope = {
    a: 3,
    b: 4
math.evaluate('a * b', scope)           // 12
math.evaluate('c = 2.3 + 4.5', scope)   // 6.8

Now, these two libraries will help you save your mathematical expression as a string config, evaluate it on both Unity client and Nodejs server.