proposition: Fact fmod_addrA : associative fmod_add.
proof: Proof. by move=> u v w; apply: val_inj; apply: mulgA. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div choice fintype bigop ssralg finset fingroup) mathcomp(morphism perm finalg action gproduct commutator) mathcomp(cyclic)