[Agda] Fin n -> Fin n extensional?

[Dan Licata]

Can you even do this (without otherwise assuming function extensionality)?

For example, for Fin 0, isn't it the same as saying "any function from 0 to A is abort":

  data Id {A : Set} (a : A) : A → Set where
    refl : Id a a

  data Void : Set where

  abort : {A : Set} → Void → A
  abort ()

  void-ext : {A : Set} → (f : Void → A) → Id f abort
  void-ext f = {!!}

(void-ext is sufficient; is it necessary?)
and if so, can you prove that?  I don't see how off the top of my head.  

-Dan

On Feb 18, 2015, at 10:47 AM, João Paulo Pizani Flor <J.P.PizaniFlor at uu.nl> wrote:

> Not yet (couldn't find it anywhere), but I will probably need it for my Ph.D project, so maybe it will come in some time...
> 
> Cheers,
> 
> João Pizani, M.Sc <j.p.pizaniflor at uu.nl>
> Promovendus - Departement Informatica
> Faculteit Bètawetenschappen - Universiteit Utrecht
> 
> On Wed, Feb 18, 2015 at 3:25 PM, Jacques Carette <carette at mcmaster.ca> wrote:
> Does anyone have a proof in Agda that functions at type (Fin n -> Fin n) are extensional?
> Jacques
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