proposition: Lemma foqcs_f r r' f: equivalence r -> equivalence r' -> function f -> source f = substrate r -> target f = substrate r' -> function (fun_on_quotients r r' f).
proof: Proof. rewrite/fun_on_quotients=> er er' ff sf tf. by apply: compf_f; apply: foqcs_axioms. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)