Add incomplete note on co-inductive natural numbers.
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-- Definition of FOTC Conat using Agda's co-inductive combinators
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{-# OPTIONS --allow-unsolved-metas #-}
{-# OPTIONS --no-universe-polymorphism #-}
{-# OPTIONS --without-K #-}

module FOT.FOTC.Data.Conat.ConatSL where

open import FOTC.Base
open import Coinduction

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data Conat : D → Set where
  cozero : Conat zero
  cosucc : ∀ {n} → (∞ (Conat n)) → Conat (succ₁ n)

Conat-unf : ∀ {n} → Conat n → n ≡ zero ∨ (∃[ n' ] Conat n' ∧ n ≡ succ₁ n')
Conat-unf cozero = inj₁ refl
Conat-unf (cosucc {n} Cn) = inj₂ (n , ♭ Cn , refl)

Conat-pre-fixed : ∀ {n} →
                  (n ≡ zero ∨ (∃[ n' ] Conat n' ∧ n ≡ succ₁ n')) →
                  Conat n
Conat-pre-fixed (inj₁ h) = subst Conat (sym h) cozero
Conat-pre-fixed (inj₂ (n , Cn , h)) = subst Conat (sym h) (cosucc (♯ Cn))

Conat-coind : ∀ (A : D → Set) {n} →
              (A n → n ≡ zero ∨ (∃[ n' ] A n' ∧ n ≡ succ₁ n')) →
              A n → Conat n
Conat-coind A h An = {!!}