proposition: Lemma dist : distributive (S:=R) cr_mult (cr_plus R).
proof: Proof. elim (cr_proof R); auto. Qed.
imports: CoRN.tactics.CornTac CoRN.algebra.CSums CoRN.algebra.CAbMonoids Coq.Sorting.Permutation CoRN.util.SetoidPermutation Coq.Setoids.Setoid Coq.Classes.Morphisms Coq(Lia)