Syntax issue when creating a multi variable User Function

Colin MacDonald_ved7w9

I have been trying to create a User Function with the Formulae section of columns.

The traditional way doesn't work at all:
WITH test(a,b) = a * b :

One variable functions with this syntax do work:

WITH test = a -> a * a:

I have then tried the same with multi variables but I can't get it to work:

I can not figure out what I am doing wrong.

 

Colin MacDonald_ved7w9

Ok, this is a version issue. I am trying to do things in 6.4 while looking at 7.1 documentation.