[Agda] type of []

[Thorsten Altenkirch]

Not sure what is the "regular" way but could you not just supply the implicit argument to [] (or to take)?

take-n-[] :  ∀ {α} {A : Set α} {n} → take n ([] {A}) ≡ []

or

take-n-[] :  ∀ {α} {A : Set α} {n} → take {A} n [] ≡ []


On 17/04/2018, 13:45, "Agda on behalf of Sergei Meshveliani" <agda-bounces at lists.chalmers.se on behalf of mechvel at botik.ru> wrote:

    People,
    
    In the proof
    
      take-n-[] :  {n : ℕ} → take n [] ≡ []
      take-n-[] {0}     =  refl
      take-n-[] {suc _} =  refl
    
    Agda cannot derive the type of []. 
    I can fix the signature in two ways.
    
      (I)
      take-n-[] :  ∀ {α} {A : Set α} {n}  → let []A : List A  -- lenghty   
                                                []A = []
                                            in 
                                            take n []A ≡ []
    
      (II)
      El : ∀ {a} (A : Set a) → A → A    -- for common usage
      El A x = x                        --
                                        --
      syntax El A x = x ∈: A            --
    
      take-n-[] :  ∀ {α} {A : Set α} {n} → take n ([] ∈: List A) ≡ []
    
    What is a regular approach, please?
    
    ------
    Sergei
    
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