Is it not:
noLeak :: State Int () noLeak = do a <- get *>* * let a' = (a + 1) a' `seq` put a'* noLeak
??
2011/6/9 Alexey Khudyakov
Hello café!
This mail is literate haskell
I have some difficulties with understanding how bang patterns and seq works.
{-# LANGUAGE BangPatterns #-} import Control.Monad import Control.Monad.Trans.State.Strict
leak :: State Int () leak = do a <- get put (a+1) leak
This function have obvious space leak. It builds huge chain of thunks so callling `runState leak 0' in ghci will eat all memory. Fix is trivial - add bang pattern. However I couldn't achieve same effect with seq. How could it be done?
noLeak :: State Int () noLeak = do a <- get let !a' = (a + 1) put a' noLeak
Thanks.
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