[Haskell-cafe] Shouldnt this be lazy too?

[Philippa Cowderoy]

On Mon, 24 Sep 2007, Vimal wrote:

> Hi all,
> 
> I was surprised to find out that the following piece of code:
> 
> > length [1..] > 10
> 
> isnt lazily evaluated! I wouldnt expect this to be a bug, but
> in this case, shouldnt the computation end when the length function
> evaluation goes something like:
> 
> > 10 + length [11..]
> 
> ?
> 

If you used genericLength and had it returning this type with an 
appropriate Num instance:

data Nat = Zero | Succ Nat

then it'd be sufficiently lazy. As it is, an Int is something you either 
have or don't - you can't only evaluate "is it less than x" without having 
to fully evaluate it.

-- 
flippa at flippac.org

"The reason for this is simple yet profound. Equations of the form
x = x are completely useless. All interesting equations are of the
form x = y." -- John C. Baez