+-- |Yet another parser combinator. This is mostly a subset of Parsec
+-- but there are some differences:
+--
+-- * This parser works on ByteString instead of String.
+--
+-- * Backtracking is the only possible behavior so there is no \"try\"
+-- action.
+--
+-- * On success, the remaining string is returned as well as the
+-- parser result.
+--
+-- * You can choose whether to treat reaching EOF (trying to eat one
+-- more letter at the end of string) a fatal error or to treat it a
+-- normal failure. If a fatal error occurs, the entire parsing
+-- process immediately fails without trying any backtracks. The
+-- default behavior is to treat EOF fatal.
+--
+-- In general, you don't have to use this module directly.
module Network.HTTP.Lucu.Parser
- ( Parser(..)
+ ( Parser
, ParserResult(..)
- , parse -- Parser a -> ByteString -> (ParserResult a, ByteString)
- , parseStr -- Parser a -> String -> (ParserResult a, ByteString)
-
- , anyChar -- Parser Char
- , eof -- Parser ()
- , allowEOF -- Parser a -> Parser a
- , satisfy -- (Char -> Bool) -> Parser Char
- , char -- Char -> Parser Char
- , string -- String -> Parser String
- , (<|>) -- Parser a -> Parser a -> Parser a
- , oneOf -- [Char] -> Parser Char
- , digit -- Parser Char
- , hexDigit -- Parser Char
- , notFollowedBy -- Parser a -> Parser ()
- , many -- Parser a -> Parser [a]
- , many1 -- Parser a -> Parser [a]
- , manyTill -- Parser a -> Parser end -> Parser [a]
- , many1Till -- Parser a -> Parser end -> Parser [a]
- , count -- Int -> Parser a -> Parser [a]
- , option -- a -> Parser a -> Parser a
- , sepBy -- Parser a -> Parser sep -> Parser [a]
- , sepBy1 -- Parser a -> Parser sep -> Parser [a]
-
- , sp -- Parser Char
- , ht -- Parser Char
- , crlf -- Parser String
+ , parse
+ , parseStr
+
+ , anyChar
+ , eof
+ , allowEOF
+ , satisfy
+ , char
+ , string
+ , (<|>)
+ , oneOf
+ , digit
+ , hexDigit
+ , notFollowedBy
+ , many
+ , many1
+ , manyTill
+ , many1Till
+ , count
+ , option
+ , sepBy
+ , sepBy1
+
+ , sp
+ , ht
+ , crlf
)
where
-import Control.Monad
import Control.Monad.State
import qualified Data.ByteString.Lazy.Char8 as B
import Data.ByteString.Lazy.Char8 (ByteString)
-data Parser a = Parser {
+-- |@Parser a@ is obviously a parser which parses and returns @a@.
+newtype Parser a = Parser {
runParser :: State ParserState (ParserResult a)
}
type IsEOFFatal = Bool
-data ParserResult a = Success a
+data ParserResult a = Success !a
| IllegalInput -- 受理出來ない入力があった
| ReachedEOF -- 限界を越えて讀まうとした
deriving (Eq, Show)
-- (>>=) :: Parser a -> (a -> Parser b) -> Parser b
instance Monad Parser where
- p >>= f = Parser $ do saved@(_, isEOFFatal) <- get -- 失敗した時の爲に状態を保存
- result <- runParser p
- case result of
- Success a -> runParser (f a)
- IllegalInput -> do put saved -- 状態を復歸
- return IllegalInput
- ReachedEOF -> if isEOFFatal then
+ p >>= f = Parser $! do saved@(_, isEOFFatal) <- get -- 失敗した時の爲に状態を保存
+ result <- runParser p
+ case result of
+ Success a -> a `seq` runParser (f a)
+ IllegalInput -> do put saved -- 状態を復歸
+ return IllegalInput
+ ReachedEOF -> do unless isEOFFatal
+ $ put saved -- 状態を復歸
return ReachedEOF
- else
- do put saved
- return IllegalInput
- return = Parser . return . Success
- fail _ = Parser $ return IllegalInput
-
+ return x = x `seq` Parser $! return $! Success x
+ fail _ = Parser $! return $! IllegalInput
+-- |@'parse' p bstr@ parses @bstr@ with @p@ and returns @(result,
+-- remaining)@.
parse :: Parser a -> ByteString -> (ParserResult a, ByteString)
-parse p input = let (result, (input', _)) = runState (runParser p) (input, True)
- in
- (result, input')
-
+parse p input -- input は lazy である必要有り。
+ = p `seq`
+ let (result, (input', _)) = runState (runParser p) (input, True)
+ in
+ result `seq` (result, input') -- input' も lazy である必要有り。
+-- |@'parseStr' p str@ packs @str@ and parses it.
parseStr :: Parser a -> String -> (ParserResult a, ByteString)
-parseStr p input = parse p $ B.pack input
+parseStr p input
+ = p `seq` -- input は lazy である必要有り。
+ parse p $! B.pack input
anyChar :: Parser Char
-anyChar = Parser $ do (input, isEOFFatal) <- get
- if B.null input then
- return ReachedEOF
- else
- do let c = B.head input
- put (B.tail input, isEOFFatal)
- return (Success c)
+anyChar = Parser $!
+ do (input, isEOFFatal) <- get
+ if B.null input then
+ return ReachedEOF
+ else
+ do let c = B.head input
+ put (B.tail input, isEOFFatal)
+ return (Success c)
eof :: Parser ()
-eof = Parser $ do (input, _) <- get
- if B.null input then
- return $ Success ()
- else
- return IllegalInput
-
-
+eof = Parser $!
+ do (input, _) <- get
+ if B.null input then
+ return $ Success ()
+ else
+ return IllegalInput
+
+-- |@'allowEOF' p@ makes @p@ treat reaching EOF a normal failure.
allowEOF :: Parser a -> Parser a
-allowEOF f = Parser $ do (input, isEOFFatal) <- get
- put (input, False)
+allowEOF f = f `seq`
+ Parser $! do (input, isEOFFatal) <- get
+ put (input, False)
- result <- runParser f
+ result <- runParser f
- (input', _) <- get
- put (input', isEOFFatal)
+ (input', _) <- get
+ put (input', isEOFFatal)
- return result
+ return result
satisfy :: (Char -> Bool) -> Parser Char
-satisfy f = do c <- anyChar
+satisfy f = f `seq`
+ do c <- anyChar
unless (f c) (fail "")
return c
char :: Char -> Parser Char
-char c = satisfy (== c)
+char c = c `seq` satisfy (== c)
string :: String -> Parser String
-string str = do mapM_ char str
+string str = str `seq`
+ do mapM_ char str
return str
infixr 0 <|>
+-- |This is the backtracking alternation. There is no non-backtracking
+-- equivalent.
(<|>) :: Parser a -> Parser a -> Parser a
-f <|> g = Parser $ do saved@(_, isEOFFatal) <- get -- 状態を保存
- result <- runParser f
- case result of
- Success a -> return $ Success a
- IllegalInput -> do put saved -- 状態を復歸
- runParser g
- ReachedEOF -> if isEOFFatal then
- return ReachedEOF
- else
- do put saved
- runParser g
+f <|> g
+ = f `seq` g `seq`
+ Parser $! do saved@(_, isEOFFatal) <- get -- 状態を保存
+ result <- runParser f
+ case result of
+ Success a -> return $ Success a
+ IllegalInput -> do put saved -- 状態を復歸
+ runParser g
+ ReachedEOF -> if isEOFFatal then
+ return ReachedEOF
+ else
+ do put saved
+ runParser g
oneOf :: [Char] -> Parser Char
notFollowedBy :: Parser a -> Parser ()
-notFollowedBy p = p >>= fail "" <|> return ()
+notFollowedBy p = p `seq`
+ p >>= fail "" <|> return ()
digit :: Parser Char
many :: Parser a -> Parser [a]
-many p = do x <- p
+many p = p `seq`
+ do x <- p
xs <- many p
return (x:xs)
<|>
many1 :: Parser a -> Parser [a]
-many1 p = do ret <- many p
+many1 p = p `seq`
+ do ret <- many p
case ret of
[] -> fail ""
xs -> return xs
manyTill :: Parser a -> Parser end -> Parser [a]
-manyTill p end = many $ do x <- p
- end
- return x
+manyTill p end
+ = p `seq` end `seq`
+ many $! do x <- p
+ end
+ return x
many1Till :: Parser a -> Parser end -> Parser [a]
-many1Till p end = many1 $ do x <- p
- end
- return x
+many1Till p end
+ = p `seq` end `seq`
+ many1 $! do x <- p
+ end
+ return x
count :: Int -> Parser a -> Parser [a]
count 0 _ = return []
-count n p = do x <- p
+count n p = n `seq` p `seq`
+ do x <- p
xs <- count (n-1) p
return (x:xs)
-
+-- def may be a _|_
option :: a -> Parser a -> Parser a
-option def p = p <|> return def
+option def p = p `seq`
+ p <|> return def
sepBy :: Parser a -> Parser sep -> Parser [a]
-sepBy p sep = sepBy1 p sep <|> return []
+sepBy p sep = p `seq` sep `seq`
+ sepBy1 p sep <|> return []
sepBy1 :: Parser a -> Parser sep -> Parser [a]
-sepBy1 p sep = do x <- p
- xs <- many $ sep >> p
+sepBy1 p sep = p `seq` sep `seq`
+ do x <- p
+ xs <- many $! sep >> p
return (x:xs)
projects / Lucu.git / blobdiff