[Haskell-cafe] coerce (safe!)

[Thomas Schilling]

On 2 mar 2008, at 01.21, Krzysztof Skrzętnicki wrote:

> Well, it is simply
>
> > coerce :: a -> b
> > coerce _ = undefined
>
> so coerce is simply empty function. But still, it is possible to  
> write a function of type (a->b).
> Well, possibly I didn't write anything particularly new, but please  
> excuse me for I'm still in
> sort of a shock after I've discovered it.
>
> Yet this function reminds me how little I know so I have a question  
> for you.
> I didn't took any lectures in Category Theory (for I'm still just a  
> student, and I won't for there are none in my institute),
> but are there any good (e)books you would recommend for a (future)  
> computer scientist?

For your particular problem you might want to start with this thread  
(and the linked paper):

   http://lambda-the-ultimate.org/node/2003