[Haskell-cafe] Streaming bytes and performance

[Konstantin Litvinenko]

On 03/19/2013 10:49 PM, Konstantin Litvinenko wrote:
> {-# LANGUAGE BangPatterns #-}
>
> import Control.Monad.State.Strict
>
> data S6 = S6 !Int !Int
>
> main_6 = do
>      let r = evalState go (S6 10000 0)
>      print r
>    where
>      go = do
>          (S6 i a) <- get
>          if (i == 0) then return a else (put (S6 (i - 1) (a + i))) >> go
>
> main_7 = do
>      let r = go (S6 10000 0)
>      print r
>    where
>      go (S6 i a)
>          | i == 0 = a
>          | otherwise = go $ S6 (i - 1) (a + i)
>
> main = main_6
>
> main_6 doing constant allocations while main_7 run in constant space.
> Can you suggest something that improve situation? I don't want to
> manually unfold all my code that I want to be fast :(.

Correction - they both run in constant space, that's not a problem. The 
problem is main_6 doing constant allocation/destroying and main_7 doesn't.