proposition: Lemma rmorph_char p : p \in char R -> p \in char S.
proof: Proof. by rewrite !inE -rmorph_nat => /andP[-> /= /eqP->]; rewrite rmorph0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)