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Haskell brainfuck interpreter.
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{-# LANGUAGE OverloadedStrings #-} | |
import Data.Array.IO | |
import Data.Array.Base | |
import Control.Applicative | |
import Control.Monad.Loops | |
import Data.Either | |
import Data.Attoparsec.Char8 | |
import qualified Data.ByteString.Char8 as B | |
import System.Environment | |
type Tape = IOUArray Int Int | |
main = do | |
program <- B.readFile =<< head <$> getArgs | |
tape <- newArray (0,30000) 0 :: IO Tape | |
unsafeWrite tape 0 1 | |
either error id (parseOnly (bf tape) program) | |
bf :: Tape -> Parser (IO ()) | |
bf tape = (sequence_ <$>) . many $! | |
(takeWhile1 (== '>') >>= return . next . B.length) | |
<|> (takeWhile1 (== '<') >>= return . prev . B.length) | |
<|> (takeWhile1 (== '+') >>= return . incr . B.length) | |
<|> (takeWhile1 (== '-') >>= return . decr . B.length) | |
<|> "." .*> return output | |
<|> "," .*> return input | |
<|> whileM_ nonzero <$> ("[" .*> bf tape <*. "]") | |
<|> notChar ']' *> bf tape | |
where | |
next n = exec $! \i v -> unsafeWrite tape 0 (i + n) | |
prev n = exec $! \i v -> unsafeWrite tape 0 (i - n) | |
incr n = exec $! \i v -> unsafeWrite tape i (v + n) | |
decr n = exec $! \i v -> unsafeWrite tape i (v - n) | |
output = exec $! \i v -> putChar $! toEnum v | |
input = exec $! \i v -> getChar >>= unsafeWrite tape i . fromEnum | |
nonzero = exec $! \i v -> return $! v /= 0 | |
exec f = do | |
i <- unsafeRead tape 0 | |
v <- unsafeRead tape i | |
f i v |
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