proposition: Lemma leifBLR x y z C : (x - y <= z ?= iff C) = (x <= z + y ?= iff C).
proof: Proof. by rewrite /leif !eq_le lerBlDr lerBrDr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)