You can use the following API to evaluate an expression
  
	public static Object evaluate(String expression) {
		...
	} 
	public static Object evaluate(String language, String expression) {
		...
	}
The following code fragment shows how to evaluate expressions in ALH API
result = ALH.evaluate("a+b");
ALH.setValue($context$, "display", result);
If no language is defined, the default language will be used (JavaScript).