proposition: Lemma insertC2 j i v a : insert j v (insert i v a) = insert i v (insert j v a).
proof: Proof. apply funext => k; rewrite /insert; case: ifPn => // /eqP <-{k}. by rewrite if_same. Qed.
imports: mathcomp(all_ssreflect) imonae_lib HB(structures) ihierarchy imonad_lib ifail_lib istate_lib itrace_lib imonad_transformer