A function reference is of the form "#someFunction(a,b,c)". Functions may be defined in
the context prior to the expression being evaluated or within the expression itself
using a lambda function definition. For example: Lambda function definition in an
expression: "(#max = {|x,y|$x>$y?$x:$y};max(2,3))" Calling context defined function:
"#isEven(37)". Functions may also be static java methods, registered in the context
prior to invocation of the expression.
Functions are very simplistic, the arguments are not part of the definition (right
now), so the names must be unique.