[GiNaC-devel] New .is_polynomial() method.

Dear all, I have added a method .is_polynomial() to GiNaC. Using .info(info_flags::polynomial) is not sufficient because in that case one cannot distinguish an expression that may be a polynomial in a variable but nog in another. Example: x*y*sin(y) is a polynomial in x but not in y. Hence (x*y*sin(y)).is_polynomial(x) returns true but (x*y*sin(y)).is_polynomial(lst(x,y)) returns false. I also patched the tutorial. Best, Chris