[Agda] Termination checking

[Andreas Abel]

Here you go:

https://github.com/agda/agda/commit/bde295096843265fd5386c8bba1b9104ac1e7c22

On 08.11.2014 15:05, Andreas Abel wrote:
> Agda.Termination.TermCheck:
>
> -- TODO: isSubTerm should compute a size difference (Order)
> isSubTerm :: Term -> DeBruijnPat -> Bool
> isSubTerm t p = equal t p || properSubTerm t p
>
> Maybe a good time to address this TODO... ;-)
>
> On 08.11.2014 14:57, Andreas Abel wrote:
>> The subterm checker of the termination checker is probably not working.
>>
>> It works if you use an explicit equality constraint in constructor ⟦_⟫_⟧.
>>
>>      ⟦_⟫_⟧ : ∀ {d d₁ d₂ ol l nl} {eq : d ≡ d₁ + d₂} → Subst d₁ ol l ->
>> Subst d₂ l nl -> Subst (suc d) ol nl
>>
>> lookup .(suc d) v       (⟦_⟫_⟧ {d} {eq = eq} ρ σ) = lookup d v (_⟫_ {eq
>> = eq} ρ σ)
>>
>> Full code attached.
>>
>>
>> On 08.11.2014 14:10, Francesco Mazzoli wrote:
>>> mutual
>>>    data Tm (l : ℕ) : Set where
>>>      var   : Fin l -> Tm l
>>>      _·_   : Tm l -> Tm l -> Tm l
>>>      lam   : Tm (suc l) -> Tm l
>>>      ⟦_,_⟧ : ∀ {d ol} -> Tm ol -> Subst d ol l -> Tm l
>>>
>>>    data Subst : (d : ℕ)(ol : ℕ)(nl : ℕ) -> Set where
>>>      id    : ∀ {ol} -> Subst 0 ol ol
>>>      _∷_   : ∀ {d ol nl} -> Tm nl -> Subst d ol nl -> Subst d (suc
>>> ol) nl
>>>      ⟦_⟫_⟧ : ∀ {d₁ d₂ ol l nl} -> Subst d₁ ol l -> Subst d₂ l nl ->
>>> Subst (suc (d₁ + d₂)) ol nl
>>>
>>> _⟫_ : ∀ {d₁ d₂ ol l nl} -> Subst d₁ ol l -> Subst d₂ l nl -> Subst (d₁
>>> + d₂) ol nl
>>> id ⟫ σ = σ
>>> (t ∷ ρ) ⟫ σ = ⟦ t , σ ⟧ ∷ (ρ ⟫ σ)
>>> _⟫_ .{suc (d₁ + d₂)} {d₃} {ol} {_} {nl} (⟦_⟫_⟧ {d₁} {d₂} ρ σ) γ =
>>>    subst (λ d → Subst d ol nl) (lm d₁ d₂ d₃) (ρ ⟫ ⟦ σ ⟫ γ ⟧)
>>>    where
>>>      lm : ∀ n m k -> n + suc (m + k) ≡ suc (n + m + k)
>>>      lm zero m k = refl
>>>      lm (suc n) m k = cong suc (lm n m k)
>>>
>>> lookup : ∀ {ol nl} d -> Fin ol -> Subst d ol nl -> Tm nl
>>> lookup .0               v       id                    = var v
>>> lookup d                zero    (t ∷ ρ)               = t
>>> lookup d                (suc v) (t ∷ ρ)               = lookup d v ρ
>>> lookup .(suc (d₁ + d₂)) v       (⟦_⟫_⟧ {d₁} {d₂} ρ σ) = lookup (d₁ +
>>> d₂) v (ρ ⟫ σ)
>>
>>
>>
>>
>>
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>> Agda at lists.chalmers.se
>> https://lists.chalmers.se/mailman/listinfo/agda
>>
>
>


-- 
Andreas Abel  <><      Du bist der geliebte Mensch.

Department of Computer Science and Engineering
Chalmers and Gothenburg University, Sweden

andreas.abel at gu.se
http://www2.tcs.ifi.lmu.de/~abel/