17 lines
758 B
Text
17 lines
758 B
Text
-- Copyright (c) 2014 Microsoft Corporation. All rights reserved.
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-- Released under Apache 2.0 license as described in the file LICENSE.
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-- Author: Leonardo de Moura
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import logic.wf data.nat.basic
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namespace well_founded
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-- This is an auxiliary definition that useful for generating a new "proof" for (well_founded R)
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-- that allows us to use well_founded.fix and execute the definitions up to k nested recursive
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-- calls without "computing" with the proofs in Hwf.
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definition intro_k {A : Type} {R : A → A → Prop} (Hwf : well_founded R) (k : nat) : well_founded R :=
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well_founded.intro
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(nat.rec_on k
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(λ n : A, well_founded.apply Hwf n)
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(λ (k' : nat) (f : Πa, acc R a), (λ n : A, acc.intro n (λ y H, f y))))
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end well_founded
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