[GiNaC-list] bug with is_polynomial?

[Jonathan Cross]

Hello,

I'm using GiNaC 1.4.3 built on Mac OS X.
I think I've found a problem with is_polynomial when powers are  
involved.

When there is an expression involving a non-integer power---even when
the expression is independent of the dummy variable of the polynomial---
then the expression is not considered a polynomial by GiNaC.

The following code illustrates the problem: (or perhaps I don't
fully understand "is_polynomial"?)

-------------------------
#include <iostream>
#include <ginac/ginac.h>

using namespace std;

int main()
{
   GiNaC::symbol x("x");
   GiNaC::symbol s("s");

   // here are two expressions that are both polynomials with respect  
to s.
   GiNaC::ex    expr1 = sin(x) + 2*s;
   GiNaC::ex    expr2 = pow(2,x) + 2*s;

   // works as expected
   if (expr1.is_polynomial(s))
     cout << expr1 << " is a polynomial with respect to " << s << endl;
   else
     cout << expr1 << " is NOT a polynomial with respect to " << s <<  
endl;

   // reports 2^x + 2s is not a polynomial in s?
   if (expr2.is_polynomial(s))
     cout << expr2 << " is a polynomial with respect to " << s << endl;
   else
     cout << expr2 << " is NOT a polynomial with respect to " << s <<  
endl;

   return 0;
}
------------------------

I'm not familiar enough with the internal workings of GiNaC to make a
patch, but this seems like the changes required would be fairly small.

Thanks!