proposition: Lemma precoeff_cat x s1 s2 : precoeff x (s1 ++ s2) = precoeff x s1 + precoeff x s2.
proof: Proof. by rewrite !precoeffE prelift_cat. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order generic_quotient) mathcomp(ssralg ssrnum ssrint)