proposition: Lemma gcdr_addl_r c a b : a %| b -> gcdr a (b + c) %= gcdr a c.
proof: Proof. by move=> hab; rewrite addrC gcdr_addr_r. 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