Re: [Haskell-cafe] Streaming bytes and performance

19 Mar 2013


      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.