arg-order of test-fn for #'position

[uhbecker@faui01.informatik.uni-erlangen.de (Ulrich Becker)]

I need to find the position of the first item in a list of numbers
that is smaller than a given number. I thought it might be possible 
to use the position-function for this purpose, using it that way:

(position given-number list-of-numbers :test #'>)

This of course works only if given-number is the first arg and 
the item in list-of-numbers is the second arg passed to the 
test-function (which is true for MCL). My question is: Is this true 
for all CL implementations, or is the ordering of arguments passed 
to the test-function implementation-dependent?

Thanks for any hints

Ulrich