proposition: Lemma left_mono (M N L : {fpmod R}) (phi : 'Mor(M,N)) (psi : 'Mor(N,L)) : is_mono (phi ** psi) -> is_mono phi.
proof: Proof. by move=> mmono K kapa /(eqmorMr psi); rewrite mul0mor -mulmorA => /mmono. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype perm choice matrix bigop zmodp mxalgebra poly) ssrcomplements stronglydiscrete coherent edr