On Thu, 6 Sep 2007, Axel Gerstenberger wrote:
module Main where
import System.IO
import Text.Printf
main :: IO ()
main = do
let all_results1 = take 20000 $ step [1]
--print $ length all_results1 -- BTW: if not commented out,
-- all values of all_results
-- are already
-- calculated here
loop [1..50] $ \i -> do
let x = all_results1!!i
putStrLn $ show i ++ " " ++ show x
The guilty thing is (!!). Better write
loop all_results1 $ \x -> do
putStrLn $ show i ++ " " ++ show x
In your program, the reference to the beginning of the list all_results1
is kept throughout the loop and thus the garbage collector cannot free the
memory.
('loop' is available as 'forM_' in GHC-6.6
http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-Monad.html#v%3AforM_)
See also:
http://www.haskell.org/haskellwiki/Things_to_avoid#Lists_are_not_arrays
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