[Axiom-developer] [#191 exquo and therefore gcd cannot handle UP(x, EXPR INT)] plausible explanation

[wyscc]

Changes 
http://page.axiom-developer.org/zope/mathaction/191ExquoAndThereforeGcdCannotHandleUPXEXPRINT/diff
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The problem is 

\begin{axiom}
r := simplify (x-2^a)*(x+2^a)
gcd(p,r)
\end{axiom}
ends up in EXPR INT, not 'UP(x,EXPR INT)' which is entirely reasonable. But 
then the 'x' in 'r' is no longer the same 'x' in p and hence the 'gcd(p,r)' is 
1. 

I don't think anything should be fixed. Users are responsible when they mix 
variables in nested polynomial domains. Check out the code for 
triangularSystems where careful pushing and pulling of these variables are done.
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forwarded from http://page.axiom-developer.org/zope/mathaction/address@hidden