Thanks Tom, with lots of trial and error I believe I finally put the exclamation marks in the right spots, but I still don't understand. addLgr (lgr1) (lgr2) = Lgr lgr where lgr tev dom = let (!(log1', lgr1')) = runLogger lgr1 tev dom (!(log2', lgr2')) = runLogger lgr2 tev dom (!log') = log1' <> log2' in (log', addLgr lgr2' lgr1') I had previously put the marks inside the tuples as in (!log1', !lgr1') but that didn't help. Can someone explain the difference between (!log1', !lgr1') and !(log1', lgr1'). I thought the former enforces more strictness than the later, but I must be missing something. Am 11/14/2015 um 01:43 PM schrieb Tom Ellis:
On Sat, Nov 14, 2015 at 01:28:58PM +0100, martin wrote:
newtype Condition a = Cnd {checkCnd :: a -> (Bool, Condition a)}
-- | Create a 'Condition' from two conditions which holds when one of -- them holds. cor :: Condition a -> Condition a -> Condition a cor c1 c2 = Cnd cnd where cnd a = let (b1', c1') = checkCnd c1 a (b2', c2') = checkCnd c2 a in if b1' || b2' then (True, cor c1' c2') else (False, cor c1 c2)
logWhen :: Monoid log => Condition (Timed evt,dom) -> Logger evt dom log -> Logger evt dom log logWhen cnd lgrIn = Lgr lgr' where lgr' tev dom = case checkCnd cnd (tev, dom) of (True, cnd') -> let (log', lgrIn') = runLogger lgrIn tev dom in (log', logWhen cnd' lgrIn') (False,cnd') -> (mempty, logWhen cnd' lgrIn)
Am I holding on to some data where I shouldn't? I cannot see it.
Sure, this
(log', lgrIn') = runLogger lgrIn tev dom
allocates a thunk for log' that holds on to tev and dom. Even if they are small, holding onto them for thousands or millions of iterations is going to leak a lot of space.
The only way to avoid this is to force log' sufficiently far that tev and dom can be released.
Tom _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe