On Mon, 7 Jul 2008 15:04:17 -0500
"William Neumann" <wneumann@gmail.com> wrote:

> For a quick hint as to why you cannot write such a function, ask
> yourself what the type of f would be.
> 
> Consider just the two cases of the type of (f 1) and (f 2).

Thanks for your swift answer,

So it's 'No', as I guessed, because the types of your two cases are different.

After Coq, maybe could we program this in Lisp ?

Regards,

Fabrice