proposition: Lemma gcdp_addl m n : gcdp m (m + n) %= gcdp m n.
proof: Proof. by rewrite -[m in m + _]mul1r gcdp_addl_mul. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop ssralg poly)