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module Main where
import System.Environment
import System.Exit
import Data.Char
type Stackelem = Integer
booltoint :: (Integral a) => Bool -> a
booltoint False = 0
booltoint True = 1
parenpairs :: String -> [(Int,Int)]
parenpairs = go 0 []
where go _ [] [] = []
go i st ('[':cs) = go (i+1) (i:st) cs
go i (s:st) (']':cs) = (s,i) : go (i+1) st cs
go i [] (']':cs) = error "rip -- unmatched closing bracket"
go i st (_:cs) = go (i+1) st cs
go _ (_:_) [] = error "rip -- unmatched open bracket"
-- returns the resulting stack
-- rip: Rip InterPreter (recursive acronym)
rip :: String -> IO [Stackelem]
rip s = rip' s []
rip' :: String -> [Stackelem] -> IO [Stackelem]
rip' [] st = return st
rip' (x:xs) st = case x of
n | '0' <= n && n <= '9' ->
rip' xs (fromIntegral (ord n - ord '0') : st)
'p' ->
rip' xs (tail st)
's' ->
rip' xs (b:a:cs)
where (a:b:cs) = st
'D' ->
rip' xs (head st : st)
'i' ->
rip' xs (head st + 1 : tail st)
'd' ->
rip' xs (head st - 1 : tail st)
'r' ->
rip' xs res
where
n = head st
newst = tail st
(begin, rest) = (take (fromIntegral n) newst, drop (fromIntegral n) newst)
res = tail begin ++ head begin : rest
'+' ->
rip' xs (a + b : cs)
where (b:a:cs) = st
'-' ->
rip' xs (a - b : cs)
where (b:a:cs) = st
'*' ->
rip' xs (a * b : cs)
where (b:a:cs) = st
'/' ->
rip' xs (a `div` b : cs)
where (b:a:cs) = st
'>' ->
rip' xs (booltoint (a > b) : cs)
where (b:a:cs) = st
'<' ->
rip' xs (booltoint (a < b) : cs)
where (b:a:cs) = st
'=' ->
rip' xs (booltoint (a == b) : cs)
where (b:a:cs) = st
'I' ->
if head afterwhite /= '['
then error "rip -- no block following I"
else if head st /= 0
then do
newstack <- rip' inblock (tail st)
rip' afterblock newstack
else rip' afterblock st
where
afterwhite = dropWhile isSpace xs
parens = parenpairs afterwhite
mainpair = minimum parens
blockend = snd mainpair
inblock = drop 1 $ take blockend afterwhite
afterblock = drop (blockend + 1) afterwhite
'W' ->
if head afterwhite /= '['
then error "rip -- no block following W"
else if head st /= 0
then do
newstack <- doloop (tail st)
rip' afterblock newstack
else rip' afterblock (tail st)
where
afterwhite = dropWhile isSpace xs
parens = parenpairs afterwhite
mainpair = minimum parens
blockend = snd mainpair
inblock = drop 1 $ take blockend afterwhite
afterblock = drop (blockend + 1) afterwhite
doloop st = do
newstack <- rip' inblock st
if head newstack /= 0
then doloop $ tail newstack
else return newstack
'o' -> do
putStr [chr (fromIntegral $ head st)]
rip' xs (tail st)
'O' -> do
putStr $ show (head st)
rip' xs (tail st)
'S' -> do
print st
rip' xs st
c | isSpace c ->
rip' xs st
_ -> do
putStr "(error) Stack: "
print st
ioError (userError $ "Unknown command '" ++ [x,'\''])
main :: IO ()
main = do
argv <- getArgs
if length argv /= 1
then do
putStrLn "Pass a rip file as the command-line argument"
exitFailure
else do
source <- readFile (argv !! 0)
rip source
return ()
|
