[Haskell-cafe] Haskell and "memoization"

[Gregory Crosswhite]

Hmm, you raise an 
On Dec 15, 2009, at 8:28 PM, Daniel Fischer wrote:

> Am Mittwoch 16 Dezember 2009 05:08:39 schrieb Gregory Crosswhite:
> 
> Not even then, necessarily. And it's not always a good idea.
> 
> f k = [1 .. 20^k]
> 

You raise a really good point here.  One can force sharing, as I understand it, by using a let clause:

n =
	let xs = f 20
	in length (xs ++ xs)

If I understand correctly, this should cause xs to be first evaluated, and then cached until the full length is computed, which in this case is obviously undesirable behavior.

Cheers,
Greg