Petter Egesund
I load my file in one chunk, and does a lot of substitutes on the string - this is quick eating all my memory and the computers start to get really slow.
Keep in mind that Strings are lists of characters. I think (somebody correct me if I'm wrong) GHC will store a character inside a cons cell, but that still leaves 8 bytes per character. Worst case it will store the 8-byte cons cell pointing to a 32-bit char value, 12 bytes per character. (Strings as lists-of-char is very useful, but not terribly efficient). Using hGetArray to read into a UArray of Word8, or something like that, will probably be a lot faster and save a lot of space.
The problem is of course that the string is copied each time I do a substitute
As W.J. says, you should make sure that you don't keep more references to the original string than you need to, so that old stuff can be garbage collected. If you post (pieces of) the code, people may be able to point out improvements more easily. -kzm -- If I haven't seen further, it is by standing in the footprints of giants