[Haskell-cafe] space leak when repeatedly calling Control.Monad.State.Strict.modify
yves.pares at gmail.com
Mon Jan 30 09:47:21 CET 2012
Have you tried to compile your code with optimisations? I guess GHC's
strictness analysis would find strict evaluation is better here.
2012/1/30 Joey Hess <joey at kitenet.net>
> Claude Heiland-Allen wrote:
> > Control.Monad.State.Strict is strict in the actions, but the state
> > itself is still lazy, so you end up building a huge thunk in the
> > state containing all the updates that ever took place to the initial
> > state.
> > Using this should fix it:
> > modify' :: MonadState s m => (s -> s) -> m ()
> > modify' f = do
> > x <- get
> > put $! f x -- force the new state when storing it
> So, why does Control.Monad.State.Strict.modify not do that?
> And, I still don't quite understand why this only happened
> when the updated value is obtained using IO.
> see shy jo
> Haskell-Cafe mailing list
> Haskell-Cafe at haskell.org
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