proposition: Lemma left_inverse_composeC (a b c:Set) (f:a->b) (f':b->c)(r:b->a)(r':c->b): is_left_inverseC f' r' -> is_left_inverseC f r -> is_left_inverseC (f' \o f) (r \o r').
proof: Proof. by move=> le' le x;rewrite !composeC_ev (left_i_v (f x) le') (left_i_v x le). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)