NNI to SingleInteger

Hello,

does somebody know the proper method/function to convert between

NNI, PI, SingleInteger, Integer

Complete conversion graph would be interesting.
Note that I am *not* interested in interpreter stuff. I want to know the 
explicit functions that I have to call in a .as file, i.e. the functions 
should live inside libaxiom.al. If possible I want to avoid the use of 
"pretend".

Yesterday, I have tried

coerce: % -> PrimitiveArray S;

from Tuple(S), but the Aldor compiler doesn't seem to know that this 
coercion exists. Any hints?

Furthermore, Tuple in Axiom has the function "select" for accessing the 
n-th element of the tuple. Unfortunately, "select" is a reserved keyword 
in Aldor. What should I do?

Thank you in advance.

Ralf