On Tue, Jun 21, 2011 at 2:24 PM, pipoca <eliyahu.ben.miney@gmail.com> wrote:

On Jun 21, 4:57 pm, Alexey Khudyakov <alexey.sklad...@gmail.com>
wrote:

> Types may be same.
>
> oops :: Int :+: Int -> Int
> oops <Int i> = mmm which one?

If you were to have your anonymous sum types be a union instead of the
disjoint union, then you could say that A :+: A has no meaning.

That sort of union would not be parametric, and would play havoc with generic programming.

E.g. consider taking a list [(t,Int)] and [(t,a)] and generating a list of [(t,Int :+: a)], then processing this with a function of the form Int -> Bool.