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Since the java version used in GroIMP does not yet support the java lambda functions, GroIMP comes with a set of own lambda functions. A Lambda function or anonymous function is a function that is not connected to an identifier and can be handled like a variable.

The XL implementation is mostly designed for mathematical or logical operations and follows a clear but strict syntax: For instance the mathematical expression f(x)=x*0.7 could be defined by this expresison: IntToFloat f = int x ⇒ float x*0.7;, This can then be use to evaluate the function for a given integer to return a float: f.evaluateFloat​(3).

This implementation is provided for any combination of the common data types (e.g. float, int, char, boolean, object) as well as for VoidTo<data type> (in this case no input parameter is needed) A full list can be found int the javadoc.

In the following a very simple example shows one possible use case of these functions, providing different mathematical calculations for instance of the same module in one rule:

module A(float len, FloatToFloat calc) extends Sphere(0.1)
{
	{setShader(GREEN);}
}
 
FloatToFloat l = float x => float x*1.2;
FloatToFloat m = float x => float x*0.7;
 
protected void init ()
[
	Axiom ==> F(1) [RU(30) RH(90)A(0.5,l)] [RU(-30) RH(90)A(0.5,m)];
]
 
public void run ()
[
	A(x,calc) ==> F(x) [RU(30) RH(90) A(calc.evaluateFloat(x),calc)] [RU(-30) RH(90) A(calc.evaluateFloat(x),calc)];
]