proposition: Lemma fscompA : associative fsfun_comp.
proof: Proof. by move=> f g h; apply/fsfunP => k; rewrite !fscompE /= !fscompE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)