( Parser
, ParserResult(..)
+ , failP
+
, parse
, parseStr
, notFollowedBy
, many
, many1
- , manyTill
- , many1Till
, count
, option
, sepBy
)
where
-import Control.Monad.State
+import Control.Monad.State.Strict
import qualified Data.ByteString.Lazy.Char8 as B
import Data.ByteString.Lazy.Char8 (ByteString)
+
-- |@Parser a@ is obviously a parser which parses and returns @a@.
newtype Parser a = Parser {
runParser :: State ParserState (ParserResult a)
}
-type ParserState = (ByteString, IsEOFFatal)
-type IsEOFFatal = Bool
+data ParserState
+ = PST {
+ pstInput :: ByteString
+ , pstIsEOFFatal :: !Bool
+ }
+ deriving (Eq, Show)
+
data ParserResult a = Success !a
| IllegalInput -- 受理出來ない入力があった
-- (>>=) :: 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
+ p >>= f = Parser $! do saved <- 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)
+ Success a -> 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
+ ReachedEOF -> do put saved -- 状態を復歸
return ReachedEOF
return x = x `seq` Parser $! return $! Success x
fail _ = Parser $! return $! IllegalInput
+-- |@'failP'@ is just a synonym for @'Prelude.fail Prelude.undefined'@.
+failP :: Parser a
+failP = fail undefined
+
-- |@'parse' p bstr@ parses @bstr@ with @p@ and returns @(result,
-- remaining)@.
parse :: Parser a -> ByteString -> (ParserResult a, ByteString)
parse p input -- input は lazy である必要有り。
= p `seq`
- let (result, (input', _)) = runState (runParser p) (input, True)
+ let (result, state') = runState (runParser p) (PST input True)
in
- result `seq` (result, input') -- input' も lazy である必要有り。
+ result `seq` (result, pstInput state') -- pstInput state' も lazy である必要有り。
-- |@'parseStr' p str@ packs @str@ and parses it.
parseStr :: Parser a -> String -> (ParserResult a, ByteString)
anyChar :: Parser Char
anyChar = Parser $!
- do (input, isEOFFatal) <- get
+ do state@(PST input _) <- get
if B.null input then
return ReachedEOF
else
- do let c = B.head input
- put (B.tail input, isEOFFatal)
- return (Success c)
+ do put $! state { pstInput = B.tail input }
+ return (Success $! B.head input)
eof :: Parser ()
eof = Parser $!
- do (input, _) <- get
+ do PST input _ <- get
if B.null input then
- return $ Success ()
+ return $! Success ()
else
return IllegalInput
-- |@'allowEOF' p@ makes @p@ treat reaching EOF a normal failure.
allowEOF :: Parser a -> Parser a
allowEOF f = f `seq`
- Parser $! do (input, isEOFFatal) <- get
- put (input, False)
+ Parser $! do saved@(PST _ isEOFFatal) <- get
+ put $! saved { pstIsEOFFatal = False }
result <- runParser f
- (input', _) <- get
- put (input', isEOFFatal)
+ state <- get
+ put $! state { pstIsEOFFatal = isEOFFatal }
return result
satisfy :: (Char -> Bool) -> Parser Char
satisfy f = f `seq`
do c <- anyChar
- unless (f c) (fail "")
- return c
+ if f c then
+ return c
+ else
+ failP
char :: Char -> Parser Char
(<|>) :: Parser a -> Parser a -> Parser a
f <|> g
= f `seq` g `seq`
- Parser $! do saved@(_, isEOFFatal) <- get -- 状態を保存
+ Parser $! do saved <- get -- 状態を保存
result <- runParser f
case result of
- Success a -> return $ Success a
+ Success a -> return $! Success a
IllegalInput -> do put saved -- 状態を復歸
runParser g
- ReachedEOF -> if isEOFFatal then
+ ReachedEOF -> if pstIsEOFFatal saved then
return ReachedEOF
else
do put saved
oneOf :: [Char] -> Parser Char
-oneOf = foldl (<|>) (fail "") . map char
+oneOf = foldl (<|>) failP . map char
notFollowedBy :: Parser a -> Parser ()
notFollowedBy p = p `seq`
- p >>= fail "" <|> return ()
+ (p >> failP) <|> return ()
digit :: Parser Char
if c >= '0' && c <= '9' then
return c
else
- fail ""
+ failP
hexDigit :: Parser Char
(c >= 'A' && c <= 'F') then
return c
else
- fail ""
+ failP
many :: Parser a -> Parser [a]
many1 :: Parser a -> Parser [a]
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
- = p `seq` end `seq`
- many $! do x <- p
- end
- return x
-
-
-many1Till :: Parser a -> Parser end -> Parser [a]
-many1Till p end
- = p `seq` end `seq`
- many1 $! do x <- p
- end
- return x
+ do x <- p
+ xs <- many p
+ return (x:xs)
count :: Int -> Parser a -> Parser [a]