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  1. {-# LANGUAGE FlexibleInstances #-}
  2. {-# LANGUAGE RankNTypes #-}
  3. {-# LANGUAGE MultiParamTypeClasses #-}
  4. {-# LANGUAGE UndecidableInstances #-}
  5.  
  6. import Data.STRef    (STRef, newSTRef, readSTRef, modifySTRef)
  7. import Control.Monad (when)
  8. import Control.Monad.ST (ST, runST)
  9.  
  10. class (Monad m) => NumMod l r m where
  11.   (+=) :: l -> r -> m ()
  12.   (-=) :: l -> r -> m ()
  13.   (*=) :: l -> r -> m ()
  14.  
  15. instance Num a => NumMod (STRef s a) (STRef s a) (ST s) where
  16.   a += b    = readSTRef b >>= \b -> modifySTRef a ((+) b)
  17.   a -= b    = readSTRef b >>= \b -> modifySTRef a ((+) (negate b))
  18.   a *= b    = readSTRef b >>= \b -> modifySTRef a ((*) b)
  19.  
  20. instance Num a => NumMod (STRef s a) a (ST s) where
  21.   a += b    = modifySTRef a ((+) b)
  22.   a -= b    = modifySTRef a ((+) (negate b))
  23.   a *= b    = modifySTRef a ((*) b)
  24.  
  25. var = newSTRef
  26.  
  27. def :: (forall s. ST s (STRef s a)) -> a
  28. def = \x -> runST $ x >>= readSTRef
  29.  
  30. class BooleanL b where toBool :: b -> Bool
  31. instance BooleanL Bool where toBool = id
  32. instance (Num a, Eq a) => BooleanL a where toBool n = n /= 0
  33.  
  34. while :: (BooleanL a) => STRef s a -> ST s () -> ST s ()
  35. while i st = fmap toBool (readSTRef i) >>= \p ->
  36.              when p $ st >> while i st
  37.  
  38. assert b str = when (not b) . return $ error str
  39.  
  40. factorial :: Integer -> Integer
  41. factorial n = def $ do
  42.     assert (n >= 0) "Negative factorial"
  43.     ret <- var 1
  44.     i   <- var n
  45.     while i $ do
  46.         ret *= i
  47.         i -= 1
  48.     return ret
  49.  
  50. main = print . factorial $ 1000
Success #stdin #stdout 0s 6272KB
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402387260077093773543702433923003985719374864210714632543799910429938512398629020592044208486969404800479988610197196058631666872994808558901323829669944590997424504087073759918823627727188732519779505950995276120874975462497043601418278094646496291056393887437886487337119181045825783647849977012476632889835955735432513185323958463075557409114262417474349347553428646576611667797396668820291207379143853719588249808126867838374559731746136085379534524221586593201928090878297308431392844403281231558611036976801357304216168747609675871348312025478589320767169132448426236131412508780208000261683151027341827977704784635868170164365024153691398281264810213092761244896359928705114964975419909342221566832572080821333186116811553615836546984046708975602900950537616475847728421889679646244945160765353408198901385442487984959953319101723355556602139450399736280750137837615307127761926849034352625200015888535147331611702103968175921510907788019393178114194545257223865541461062892187960223838971476088506276862967146674697562911234082439208160153780889893964518263243671616762179168909779911903754031274622289988005195444414282012187361745992642956581746628302955570299024324153181617210465832036786906117260158783520751516284225540265170483304226143974286933061690897968482590125458327168226458066526769958652682272807075781391858178889652208164348344825993266043367660176999612831860788386150279465955131156552036093988180612138558600301435694527224206344631797460594682573103790084024432438465657245014402821885252470935190620929023136493273497565513958720559654228749774011413346962715422845862377387538230483865688976461927383814900140767310446640259899490222221765904339901886018566526485061799702356193897017860040811889729918311021171229845901641921068884387121855646124960798722908519296819372388642614839657382291123125024186649353143970137428531926649875337218940694281434118520158014123344828015051399694290153483077644569099073152433278288269864602789864321139083506217095002597389863554277196742822248757586765752344220207573630569498825087968928162753848863396909959826280956121450994871701244516461260379029309120889086942028510640182154399457156805941872748998094254742173582401063677404595741785160829230135358081840096996372524230560855903700624271243416909004153690105933983835777939410970027753472000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
https://ideone.com/6Xi9ML
language:
Haskell (ghc 8.4.4)
created:
10 years ago
visibility:
secret

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