[Haskell-cafe] Shouldnt this be lazy too?

[Neil Mitchell]

Hi

> > Pretty much, yes.
> >
>
> So I just need to write
>
>   newtype LazyNatural = LazyNatural [()]

or

data Nat = Zero | Succ Nat

it's your choice really.

> and then add some suitable instances. ;-)

Yes. Lots of them. Lots of instances and lots of methods.

> Hey, the "length" function would then just be
>
>   ln_length :: [x] -> LazyNatural
>   ln_length = LazyNatural . map (const ())
>
> Ooo, that's hard.

Nope, its really easy. Its just quite a bit of work filling in all the
instances. I bet you can't do it and upload the results to hackage
within 24 hours :-)

Thanks

Neil