noteed:

Hi all,

the problem is simple but i can't do it :

I want to generate some values and 'accumulate' them. The meaning of 'accumulating' is not so important. The only point is that to 'accumulate' the values, I only have to know one value and the accumulator (and not all the values).

The most simple example is that of adding a list of numbers.

I thought that I could use a haskell list to represent the values so I could use foldr or mapM to do the accumulation (and not an imperative-style loop).

Below are four attempts to solve the problem. It's not solved : in ghci, I have '*** Exception: stack overflow' with 'test1 5000000'.

5000000 is not so much for my application.

How can I achieve what I want (and efficiently)? ---------------------------------------------------------------------}

import Control.Monad.State import Control.Monad.ST import Data.STRef

acc1, acc2, acc3 :: [Int] -> Int

----------------------------------------------------------------------

acc1 ints = foldr (+) 0 ints

Strictify the accumulator? Prelude List Data.List> foldl1 (+) (replicate 5000000 1) *** Exception: stack overflow versus Prelude List Data.List> foldl1' (+) (replicate 5000000 1) 5000000 (Redirected to haskell-cafe@) -- Don