AbstractFunction constructor
Creates a new function with given name and parameter count.
name - The name of the function.
numParams - The number of parameters for this function.
-1 denotes a variable number of parameters.
booleanFunction Whether this function is a boolean function.
Implementation
AbstractFunction(String name, int numParams, {bool booleanFunction = false})
: super(name, numParams, booleanFunction: booleanFunction);