The third (and subsequent) arguments of gcd specify the variable ordering
used (ratvars). Unfortunately, the documentation (? gcd -- cf. ? divide)
does not say this -- that should be corrected.
It is not clear to me why the variable ordering is important. Since
multivariate polynomials have unique factorization, they also have unique
GCD. The *form* of the result may be different, and the *efficiency* of
the calculation may depend on the variable ordering, but the result should
be the same (modulo units, which may be different because the gcd makes the
leading term positive).
Even when it is important, this seems like a pretty specialized case;
wouldn't it be simpler to bind ratvars locally to choose the variable
ordering, just as in the rest of the CRE package?
-s
On Fri, Nov 23, 2012 at 4:54 AM, Antonio Lapira <antoniolapira at yahoo.it>wrote:
> why gdc accepts only 2 numbers? like gdc(60,48) and not for example: gdc
> (60,48,36)?
>
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