fact: Definition pure_state {S E} : E ~> stateT S (itree E) := fun _ e s => Vis e (fun x => Ret (s, x)).
imports: ExtLib(Structures.Functor Structures.Monad) ITree(Basics.Basics Basics.CategoryOps Basics.CategoryKleisli Core.ITreeDefinition Indexed.Function Indexed.Sum Core.Subevent Interp.Interp)