proposition: Lemma eq_lrshift m n i j : (@lshift m n i == @rshift m n j) = false.
proof: Proof. apply/eqP=> /(congr1 val)/= def_i; have := ltn_ord i. by rewrite def_i -ltn_subRL subnn. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(path div)