proposition: Fact ffun_mulA : associative ffun_mul.
proof: Proof. by move=> f1 f2 f3; apply/ffunP=> i; rewrite !ffunE mulrA. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)