[Haskell-cafe] Re: foldl vs foldl'

"Daryoush Mehrtash" wrote:

Are there cases (function or list) where the result of foldl (or foldr)would be different that foldl' (or foldr')?

Yes, in two cases folds can differ: a) You've got an infinite list, in which case you don't want to go to the end of it before starting to return values b) You don't have infinite memory and thus need things to be strict (or just don't want to pay the overhead of allocating millions of thunks for no good reason whatsoever, in case you're lucky enough to have enough memory for your data) -- (c) this sig last receiving data processing entity. Inspect headers for copyright history. All rights reserved. Copying, hiring, renting, performance and/or quoting of this signature prohibited.