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Possibly working BF intepreter
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| import Text.Parsec.String (Parser) | |
| import Control.Applicative hiding ((<|>)) | |
| import Text.ParserCombinators.Parsec hiding (many) | |
| import Data.Char(chr, ord) | |
| import System.Environment | |
| data BFCmd | |
| = BFPrev | |
| | BFNext | |
| | BFInc | |
| | BFDec | |
| | BFRead | |
| | BFPrint | |
| | BFLoop [BFCmd] | |
| deriving (Show, Eq) | |
| data Tape a = Tape [a] -- Left of the pivot element | |
| a -- Pivot element | |
| [a] -- Right of the pivot element | |
| type BFProgram = [BFCmd] | |
| simpleCmds :: String | |
| simpleCmds = "<>+-,." | |
| simpleCmdP :: Parser BFCmd | |
| simpleCmdP = oneOf simpleCmds >>= f | |
| where f x = return $ case x of | |
| '<' -> BFPrev | |
| '>' -> BFNext | |
| '+' -> BFInc | |
| '-' -> BFDec | |
| ',' -> BFRead | |
| '.' -> BFPrint | |
| commentP :: Parser String | |
| commentP = many $ noneOf $ simpleCmds++"[]" | |
| bfOpP :: Parser BFCmd | |
| bfOpP = (commentP *> simpleCmdP <* commentP) <?> "" | |
| bfLoopP :: Parser BFCmd | |
| bfLoopP = between (char '['<?>"") (char ']'<?>"loop closing bracket") | |
| (commentP *> many (bfOpP <|> bfLoopP)) >>= \src -> return $ BFLoop src | |
| bfProgramP :: Parser BFProgram | |
| bfProgramP = (many (commentP *> (bfLoopP <|> bfOpP) <* commentP)) <* (eof <?> "") | |
| runBf :: BFProgram -> Tape Int -> IO () | |
| runBf prog@(cmd:cmds) tape@(Tape left@(l:ls) p right@(r:rs)) = | |
| case cmd of | |
| BFPrev -> runBf cmds $ Tape (p:left) r rs | |
| BFNext -> runBf cmds $ Tape ls l (p:right) | |
| BFInc -> runBf cmds $ Tape left (p+1) right | |
| BFDec -> runBf cmds $ Tape left (p-1) right | |
| BFRead -> getChar >>= \c -> runBf cmds $ Tape left (ord c) right | |
| BFPrint -> putChar (chr p) >> runBf cmds tape | |
| BFLoop loopBody -> if p == 0 then runBf cmds tape else runBf (loopBody++prog) tape | |
| runBf [] _ = return () | |
| main :: IO () | |
| main = do | |
| args <- getArgs | |
| src <- readFile $ case args of | |
| [] -> error "Filepath expected!!!" | |
| path:_ -> path | |
| let bfProg = parse bfProgramP "" src | |
| case bfProg of | |
| Right prog -> | |
| let zeros = repeat 0 | |
| emptyTape = Tape zeros 0 zeros | |
| in runBf prog emptyTape | |
| Left err -> print err |
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