AbstractLazyFunction 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
AbstractLazyFunction(String name, this.numParams,
{this.booleanFunction = false})
: name = name.toUpperCase();