proposition: Lemma mulmorBr (psi : 'Mor(M, N)) (phi1 phi2 : 'Mor(N, P)) : psi ** (phi1 - phi2) = psi ** phi1 - psi ** phi2.
proof: Proof. by rewrite mulmorDr mulmorN. 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