dvde:
>
> Don Stewart schrieb:
>> It is not possible to write a modifyIORef that *doesn't* leak memory!
>>
> Why? Or can one read about it somewhere?
Try writing a version of this program, using modifyIORef only,
such that it doesn't exhaust the heap:
import Data.IORef
import Control.Monad
import System.IO.Unsafe
ref :: IORef Int
ref = unsafePerformIO $ newIORef 0
{-# NOINLINE ref #-}
main = do
modifyIORef ref (\a -> a + 1)
main
Run it in a constrained environment, so you don't thrash:
$ ./A +RTS -M100M
Heap exhausted;
Current maximum heap size is 99999744 bytes (95 MB);
use `+RTS -M<size>' to increase it.
The goal is to run in constant space.
-- Don
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