proposition: Theorem Y_rel_realizer (T : Type) (R : T -> T -> Prop) (Hwf : well_founded R) (rel : T -> formula) : forall e, Y_rel↓e ⊩ ∀P, (∀x, rel x → (∀y, rel y → R y x ↦ P y) → P x) → ∀z, rel z → P z.
proof: Proof. intro. startn 2. apply (Y_realizer Hwf). exists (fun t => rel t → P t). repeat Ksolve. Qed.
imports: ClassicalRealizability.Tactics