Cabal-2.2.0.0: A framework for packaging Haskell software

Copyright (c) Edward Kmett 2011-2012 BSD3 ekmett@gmail.com experimental non-portable None Haskell2010

Distribution.Compat.Parsing

Contents

Description

Alternative parser combinators.

Originally in parsers package.

Synopsis

# Parsing Combinators

choice :: Alternative m => [m a] -> m a #

choice ps tries to apply the parsers in the list ps in order, until one of them succeeds. Returns the value of the succeeding parser.

option :: Alternative m => a -> m a -> m a #

option x p tries to apply parser p. If p fails without consuming input, it returns the value x, otherwise the value returned by p.

 priority = option 0 (digitToInt <$> digit) optional :: Alternative f => f a -> f (Maybe a) # One or none. skipOptional :: Alternative m => m a -> m () # skipOptional p tries to apply parser p. It will parse p or nothing. It only fails if p fails after consuming input. It discards the result of p. (Plays the role of parsec's optional, which conflicts with Applicative's optional) between :: Applicative m => m bra -> m ket -> m a -> m a # between open close p parses open, followed by p and close. Returns the value returned by p.  braces = between (symbol "{") (symbol "}") some :: Alternative f => forall a. f a -> f [a] # One or more. many :: Alternative f => forall a. f a -> f [a] # Zero or more. sepBy :: Alternative m => m a -> m sep -> m [a] # sepBy p sep parses zero or more occurrences of p, separated by sep. Returns a list of values returned by p.  commaSep p = p sepBy (symbol ",") sepBy1 :: Alternative m => m a -> m sep -> m [a] # sepBy1 p sep parses one or more occurrences of p, separated by sep. Returns a list of values returned by p. sepEndBy1 :: Alternative m => m a -> m sep -> m [a] # sepEndBy1 p sep parses one or more occurrences of p, separated and optionally ended by sep. Returns a list of values returned by p. sepEndBy :: Alternative m => m a -> m sep -> m [a] # sepEndBy p sep parses zero or more occurrences of p, separated and optionally ended by sep, ie. haskell style statements. Returns a list of values returned by p.  haskellStatements = haskellStatement sepEndBy semi endBy1 :: Alternative m => m a -> m sep -> m [a] # endBy1 p sep parses one or more occurrences of p, separated and ended by sep. Returns a list of values returned by p. endBy :: Alternative m => m a -> m sep -> m [a] # endBy p sep parses zero or more occurrences of p, separated and ended by sep. Returns a list of values returned by p.  cStatements = cStatement endBy semi count :: Applicative m => Int -> m a -> m [a] # count n p parses n occurrences of p. If n is smaller or equal to zero, the parser equals to return []. Returns a list of n values returned by p. chainl :: Alternative m => m a -> m (a -> a -> a) -> a -> m a # chainl p op x parses zero or more occurrences of p, separated by op. Returns a value obtained by a left associative application of all functions returned by op to the values returned by p. If there are zero occurrences of p, the value x is returned. chainr :: Alternative m => m a -> m (a -> a -> a) -> a -> m a # chainr p op x parses zero or more occurrences of p, separated by op Returns a value obtained by a right associative application of all functions returned by op to the values returned by p. If there are no occurrences of p, the value x is returned. chainl1 :: Alternative m => m a -> m (a -> a -> a) -> m a # chainl1 p op x parses one or more occurrences of p, separated by op Returns a value obtained by a left associative application of all functions returned by op to the values returned by p. . This parser can for example be used to eliminate left recursion which typically occurs in expression grammars.  expr = term chainl1 addop term = factor chainl1 mulop factor = parens expr <|> integer mulop = (*) <$ symbol "*"
<|> div <$symbol "/" addop = (+) <$ symbol "+"
<|> (-) <$symbol "-" chainr1 :: Alternative m => m a -> m (a -> a -> a) -> m a # chainr1 p op x parses one or more occurrences of p, separated by op Returns a value obtained by a right associative application of all functions returned by op to the values returned by p. manyTill :: Alternative m => m a -> m end -> m [a] # manyTill p end applies parser p zero or more times until parser end succeeds. Returns the list of values returned by p. This parser can be used to scan comments:  simpleComment = do{ string "<!--" ; manyTill anyChar (try (string "-->")) } Note the overlapping parsers anyChar and string "-->", and therefore the use of the try combinator. # Parsing Class class Alternative m => Parsing m where # Additional functionality needed to describe parsers independent of input type. Minimal complete definition Methods try :: m a -> m a # Take a parser that may consume input, and on failure, go back to where we started and fail as if we didn't consume input. (<?>) :: m a -> String -> m a infixr 0 # Give a parser a name skipMany :: m a -> m () # A version of many that discards its input. Specialized because it can often be implemented more cheaply. skipSome :: m a -> m () # skipSome p applies the parser p one or more times, skipping its result. (aka skipMany1 in parsec) unexpected :: String -> m a # Used to emit an error on an unexpected token eof :: m () # This parser only succeeds at the end of the input. This is not a primitive parser but it is defined using notFollowedBy.  eof = notFollowedBy anyChar <?> "end of input" notFollowedBy :: Show a => m a -> m () # notFollowedBy p only succeeds when parser p fails. This parser does not consume any input. This parser can be used to implement the 'longest match' rule. For example, when recognizing keywords (for example let), we want to make sure that a keyword is not followed by a legal identifier character, in which case the keyword is actually an identifier (for example lets). We can program this behaviour as follows:  keywordLet = try$ string "let" <* notFollowedBy alphaNum

Instances

 # Methodstry :: ParsecParser a -> ParsecParser a #() :: ParsecParser a -> String -> ParsecParser a #eof :: ParsecParser () #notFollowedBy :: Show a => ParsecParser a -> ParsecParser () # (Parsing m, MonadPlus m, Monoid w) => Parsing (WriterT w m) # Methodstry :: WriterT w m a -> WriterT w m a #() :: WriterT w m a -> String -> WriterT w m a #skipMany :: WriterT w m a -> WriterT w m () #skipSome :: WriterT w m a -> WriterT w m () #unexpected :: String -> WriterT w m a #eof :: WriterT w m () #notFollowedBy :: Show a => WriterT w m a -> WriterT w m () # (Parsing m, MonadPlus m, Monoid w) => Parsing (WriterT w m) # Methodstry :: WriterT w m a -> WriterT w m a #() :: WriterT w m a -> String -> WriterT w m a #skipMany :: WriterT w m a -> WriterT w m () #skipSome :: WriterT w m a -> WriterT w m () #unexpected :: String -> WriterT w m a #eof :: WriterT w m () #notFollowedBy :: Show a => WriterT w m a -> WriterT w m () # (Parsing m, MonadPlus m) => Parsing (StateT s m) # Methodstry :: StateT s m a -> StateT s m a #() :: StateT s m a -> String -> StateT s m a #skipMany :: StateT s m a -> StateT s m () #skipSome :: StateT s m a -> StateT s m () #unexpected :: String -> StateT s m a #eof :: StateT s m () #notFollowedBy :: Show a => StateT s m a -> StateT s m () # (Parsing m, MonadPlus m) => Parsing (StateT s m) # Methodstry :: StateT s m a -> StateT s m a #() :: StateT s m a -> String -> StateT s m a #skipMany :: StateT s m a -> StateT s m () #skipSome :: StateT s m a -> StateT s m () #unexpected :: String -> StateT s m a #eof :: StateT s m () #notFollowedBy :: Show a => StateT s m a -> StateT s m () # (Parsing m, Monad m) => Parsing (IdentityT * m) # Methodstry :: IdentityT * m a -> IdentityT * m a #() :: IdentityT * m a -> String -> IdentityT * m a #skipMany :: IdentityT * m a -> IdentityT * m () #skipSome :: IdentityT * m a -> IdentityT * m () #unexpected :: String -> IdentityT * m a #eof :: IdentityT * m () #notFollowedBy :: Show a => IdentityT * m a -> IdentityT * m () # (~) * t Char => Parsing (Parser r t) # Methodstry :: Parser r t a -> Parser r t a #() :: Parser r t a -> String -> Parser r t a #skipMany :: Parser r t a -> Parser r t () #skipSome :: Parser r t a -> Parser r t () #unexpected :: String -> Parser r t a #eof :: Parser r t () #notFollowedBy :: Show a => Parser r t a -> Parser r t () # (Parsing m, MonadPlus m) => Parsing (ReaderT * e m) # Methodstry :: ReaderT * e m a -> ReaderT * e m a #() :: ReaderT * e m a -> String -> ReaderT * e m a #skipMany :: ReaderT * e m a -> ReaderT * e m () #skipSome :: ReaderT * e m a -> ReaderT * e m () #unexpected :: String -> ReaderT * e m a #eof :: ReaderT * e m () #notFollowedBy :: Show a => ReaderT * e m a -> ReaderT * e m () # (Stream s m t, Show t) => Parsing (ParsecT s u m) # Methodstry :: ParsecT s u m a -> ParsecT s u m a #() :: ParsecT s u m a -> String -> ParsecT s u m a #skipMany :: ParsecT s u m a -> ParsecT s u m () #skipSome :: ParsecT s u m a -> ParsecT s u m () #unexpected :: String -> ParsecT s u m a #eof :: ParsecT s u m () #notFollowedBy :: Show a => ParsecT s u m a -> ParsecT s u m () # (Parsing m, MonadPlus m, Monoid w) => Parsing (RWST r w s m) # Methodstry :: RWST r w s m a -> RWST r w s m a #() :: RWST r w s m a -> String -> RWST r w s m a #skipMany :: RWST r w s m a -> RWST r w s m () #skipSome :: RWST r w s m a -> RWST r w s m () #unexpected :: String -> RWST r w s m a #eof :: RWST r w s m () #notFollowedBy :: Show a => RWST r w s m a -> RWST r w s m () # (Parsing m, MonadPlus m, Monoid w) => Parsing (RWST r w s m) # Methodstry :: RWST r w s m a -> RWST r w s m a #() :: RWST r w s m a -> String -> RWST r w s m a #skipMany :: RWST r w s m a -> RWST r w s m () #skipSome :: RWST r w s m a -> RWST r w s m () #unexpected :: String -> RWST r w s m a #eof :: RWST r w s m () #notFollowedBy :: Show a => RWST r w s m a -> RWST r w s m () #