proposition: Lemma sim_dec : forall x y, {sim x y}+{~ sim x y}.
proof: Proof. move => x y. rewrite /sim. case: (similar x y). by left. by right. Defined.
imports: Coq(RelationClasses Setoid Morphisms Permutation) Coq(SetoidList Mergesort Orders) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype) mathcomp(bigop path) RegLang(languages) RegexpBrzozowski(glue gfinset regexp)