[Haskell] whereis the lazyness ?

[Duncan Coutts]

On Sat, 2004-12-04 at 19:12 +0000, Jules Bean wrote:
> On 3 Dec 2004, at 19:22, Duncan Coutts wrote:
> 
> > I can't immediately think of a collection data structure combining O(1)
> > lookup with a sparse key space however - that sounds quite tricky.
> >
> 
> Hashtable, surely?

Yes of course - silly me!

I forget about hash tables because as a functional programmer I don't
use them very often since they need to be used in a monad. I wonder in
what situations a purely functional hash table based on DiffArray would
perform better than a FiniteMap.

Duncan