proposition: Lemma gcdrAC a b c : gcdr (gcdr a b) c %= gcdr (gcdr a c) b.
proof: Proof. rewrite (eqd_trans _ (gcdrA _ _ _)) // eqd_sym (eqd_trans _ (gcdrA _ _ _)) //. by rewrite (eqd_gcd _ (gcdrC _ _)) //. Qed.
imports: HB(structures) Coq(ssreflect ssrfun ssrbool Arith.Wf_nat) mathcomp(eqtype ssrnat div seq path) mathcomp(ssralg fintype perm tuple choice generic_quotient) mathcomp(matrix bigop zmodp mxalgebra poly) stronglydiscrete