[Agda] `let' in function signature

[James Wood]

Did you mean let q' = suc q, rather than suc n?

James


On 24/12/17 19:58, Sergei Meshveliani wrote:
> Please, what is wrong in the below program?
>
> ---------------------------------------------------------------
> open import Relation.Binary.PropositionalEquality using (_≡_)
> open import Data.Nat using (ℕ; suc; pred; _*_; _^_)
>
> postulate  anything : ∀ {a} {A : Set a} → A
> postulate  pSum : ℕ → ℕ	→ ℕ
>
> pSum-eq :  (q n : ℕ) → let q' = suc n
>                        in
>                        (pSum q' n) * q  ≡  pred (q' ^ (suc n))  -- (1)
> pSum-eq 1 0 =  goal
>                where
>                postulate goal :  (pSum 2 0) * 1  ≡  pred (2 ^ 1)
>
> pSum-eq _ _ =  anything
> ----------------------------------------------------------------
>
> Agda 2.5.3  reports
>
>   2 != 1 of type ℕ
>   when checking that the expression goal has type
>   pSum 1 ℕ.zero * 1 ≡ pred (1 ^ 1)
>
> After replacing  q'  with  (suc q)  in the line (1), the type check
> succeeds.
>
> Is this a bug?
>
> Regards,
>
> ------
> Sergei
>
>
>
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