fact: Definition handle_envT (X : UU0) (t : envT Z M X) (h : unit -> envT Z M X) : envT Z M X := fun e => match t e with | inl z => h z e | inr x => inr x end.
imports: mathcomp(all_ssreflect) HB(structures) imonae_lib ihierarchy imonad_lib imonad_transformer imonad_model