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{-# LANGUAGE BangPatterns #-}
-- See Trac #3403: interaction of pattern match failure and CPR
-- The point is that this should run in constant space, with no
-- stack growth. In GHC 6.10 the tail call optimisation didn't work.
module Main (main) where
import qualified Data.Set as Set
import Data.Set (Set)
data Result = Result !S1 !S2
type S1 = Set ()
type S2 = Set ()
input :: [[(Int, ())]]
input = replicate 1000 (replicate 400 (100, ()))
main :: IO ()
main = do let Result s1 s2 = doAll Set.empty Set.empty () input
print $ Set.size s1
print $ Set.size s2
doAll :: S1 -> S2 -> () -> [[(Int, ())]] -> Result
doAll !s1 !s2 !_ [] = Result s1 s2
doAll !s1 !s2 !unit ([] : xs) = doAll s1 s2 unit xs
doAll !s1 !s2 !unit (((t, _) : x1) : x2 : xs)
| t >= 99999 = doAll s1 s2 unit (x1 : x2 : xs)
doAll !s1 !s2 !unit (((_, ()) : x) : xs)
= doAll s1 s2 unit (x : xs)
|
