simp [h₂]
case Ret
E F : Type → Type
T R : Type
h : E ~> WriterT (Fitree F)
k : T → Fitree E R
r✝ : T
h₁ : ∀ (x : String), "" ++ x = x
h₂ : ∀ (α β : Type) (x : α × β), (x.fst, x.snd) = x
⊢ interp h (k r✝) = bind (interp h (k r✝)) fun x => ret (x.fst, x.snd)
no goals