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(*         *      The Rocq Prover / The Rocq Development Team           *)
(*  v      *         Copyright INRIA, CNRS and contributors             *)
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(*         *     GNU Lesser General Public License Version 2.1          *)
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(** Author: Cristina Cornes. From: Constructing Recursion Operators in Type Theory L. Paulson  JSC (1986) 2, 325-355 *)
#[universes(template)]
Inductive WO (A : Type) (B : A -> Type) : Type :=
sup : forall (a:A) (f:B a -> WO A B), WO A B.
Section WellOrdering.
Variable A : Type.
Variable B : A -> Type.
Notation WO := (WO A B).
Inductive le_WO : WO -> WO -> Prop :=
le_sup : forall (a:A) (f:B a -> WO) (v:B a), le_WO (f v) (sup _ _ a f).

(* Specifications: *)
Lemma le_WO_inv x y : le_WO x y -> exists a f v, f v = x /\ sup _ _ a f = y.
Theorem wf_WO : well_founded le_WO.
End WellOrdering.