2009/5/27 Bertram Felgenhauer <bertram.felgenha...@googlemail.com>: > I wrote: >> Krzysztof Skrzętnicki wrote: >>> The code for modifying the counter: >>> (\ msg -> atomicModifyIORef ioref (\ cnt -> (cntMsg cnt msg,()))) >> >> atomicModifyIORef does not force the new value of the IORef. >> If the previous contents of the IORef is x, the new contents >> will be a thunk, >> >> (\ cnt -> (cntMsg cnt msg,())) x > > Sorry, it's slightly worse than that. The contents becomes > > sel_0 (\ cnt -> (cntMsg cnt msg, ())) x > > where sel_0 is basically an RTS internal version of fst. > > Instead of reading the new value of the IORef, you could also force the > old one: > > atomicModifyIORef ioref (\ cnt -> (cntMsg cnt msg, msg)) >>= (return $!) >
Thanks for the tip, although it seems tricky to get it right. I wonder why there is no strict version of atomicModifyIORef? Dually there might be a strict version of IORef datatype. Best regards Christopher Skrzętnicki _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
