On Wed, Nov 16, 2011 at 12:07 PM, Johan Tibell <[email protected]>wrote:
> On Wed, Nov 16, 2011 at 11:58 AM, Jason Dusek <[email protected]>wrote: > >> diff --git a/Rebuild.hs b/Rebuild.hs >> @@ -15,6 +15,7 @@ import Data.STRef >> import Data.String >> import Data.Word >> >> +import Control.DeepSeq >> import Data.Vector.Unboxed (Vector) >> import qualified Data.Vector.Unboxed as Vector (create, length) >> import qualified Data.Vector.Unboxed.Mutable as Vector hiding (length) >> @@ -46,8 +47,8 @@ rebuildAsVector bytes = byteVector >> n <- readSTRef counter >> return (Vector.unsafeSlice 0 n v) >> writeOneByte v counter b = do n <- readSTRef counter >> - Vector.unsafeWrite v n b >> + w v n b >> modifySTRef counter (+!1) >> + (+!) a b = ((+) $!! a) $!! b >> + w v n b = (Vector.unsafeWrite v $!! n) $!! b >> > > +! doesn't work unless modifySTRef is already strict in the result of the > function application. You need to write modifySTRef' that seq:s the result > of the function application before calling writeSTRef. > Just double checked. modifySTRef is too lazy: -- |Mutate the contents of an 'STRef' modifySTRef :: STRef s a -> (a -> a) -> ST s () modifySTRef ref f = writeSTRef ref . f =<< readSTRef ref We need Data.STRef.Strict
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