proposition: Lemma ucmE i j : ucm i j = (i == j) :> nat.
proof: Proof. by rewrite cmE fsfun_fun in_fsetE; case: eqVneq. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap