template<typename
T>
struct poly_int_traits< T >
poly_int_traits<T> describes an integer type T that might be polynomial
or non-polynomial:
- poly_int_traits<T>::is_poly is true if T is a poly_int-based type
and false otherwise.
- poly_int_traits<T>::num_coeffs gives the number of coefficients in T
if T is a poly_int and 1 otherwise.
- poly_int_traits<T>::coeff_type gives the coefficent type of T if T
is a poly_int and T itself otherwise
- poly_int_traits<T>::int_type is a shorthand for
typename poly_coeff_traits<coeff_type>::int_type.