proposition: Lemma eql2n_neql : forall l1 l2, eql l1 l2 -> ~ neql l1 l2.
proof: Proof. move => l1 l2 heq hneq. by apply: (@neql2n_eql l1 l2). Qed.
imports: Coq(RelationClasses Setoid Morphisms SetoidList Mergesort Permutation) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype) mathcomp(bigop path) RegexpBrzozowski(glue)