[Haskell-beginners] Functional Data Structure with Cheapest Modification?

[Daniel Fischer]

Am Dienstag 06 April 2010 21:51:47 schrieb Daniel Fischer:
>
> An immutable array should be fine for this. When you modify one tree,
> you create a new array of 200 pointers to trees, 199 of them are just
> copied from the old array, one points to your new modified tree.
>
> Of course, with STArrays, there would be no need to copy any pointers
> and allocate new arrays, so in principle it should be even more
> efficient, but boxed mutable arrays and the garbage collector don't play
> too well together (http://hackage.haskell.org/trac/ghc/ticket/650), so
> it might not be better.

Forgot to check before posting: it's fixed now, the fix will be in 6.12.2.

And what Edward said, only pointers will be copied anyway, so a Map can 
well be better than an array, depends on your access patterns.