proposition: Lemma composable_fun_projs r r' f: equivalence r -> equivalence r' -> lf_axiom f (substrate r) (substrate r') -> (function_on_quotients r r' f) \coP (canon_proj r).
proof: Proof. move=> er er' ta. by split; [apply: foqs_f | fprops | rewrite/function_on_quotients; aw ]. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)