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这个小haskell code snippet导致GHC编译期间不会终止:一小段代码将导致GHC不终止
{-# LANGUAGE BangPatterns #-}
{-# OPTIONS_GHC -O2 #-}
import qualified Data.Vector.Unboxed.Mutable as MV
import Data.Vector.Unboxed ((!))
import qualified Data.Vector.Unboxed as V
import Control.Monad (forM_)
similar :: V.Vector Char -> Int
similar v = l + sum (map (similar' 1 1) checks)
where
(l,checks) = let h = V.head v in V.foldl'
(\(i,is) c -> if c == h then (i+1,i:is) else (i+1,is)) (1,[]) (V.tail v)
similar' !r !n !i = if i < l-1 && v!(n) == v!(i+1) then similar' (r+1) (n+1) (i+1)
else r
main :: IO()
main = do
n <- getLine
v <- MV.replicate (read n) 0
forM_ [1..read n] $ \n' -> do
v' <- getLine
MV.unsafeWrite v (n'-1) (similar . V.fromList $ v')
V.unsafeFreeze v >>= V.mapM_ print
我试图GHC 7.4.1和7.6.1两者不会终止。当我使用ByteString
s而不是Vector
s时,代码工作正常。这是ghc问题还是图书馆问题?或者在我的代码中有什么问题?
如果编译器崩溃,这是编译器的错误。 – 2013-01-06 22:59:46