Polynomial.PolyRepresentation of polonomial with rational coefficient. a1.m1 + ... + c where
val constant : NumCompat.Q.t -> tconstant c
val get : Monomial.t -> t -> NumCompat.Q.tget mi p
val fold : ( Monomial.t -> NumCompat.Q.t -> 'a -> 'a ) -> t -> 'a -> 'afold f p a folds f over the monomials of p with non-zero coefficient
val add : Monomial.t -> NumCompat.Q.t -> t -> tadd m n p