Text.Parsec

parsec-3.1.13.0: Monadic parser combinators

Copyright | (c) Daan Leijen 1999-2001 (c) Paolo Martini 2007
License | BSD-style (see the LICENSE file)
Maintainer | aslatter@gmail.com
Stability | provisional
Portability | portable
Safe Haskell | Safe
Language | Haskell2010

Text.Parsec

Contents

- Parsers
- Combinators
- Character Parsing
- Error messages
- Position
- Debugging
- Low-level operations
- Other stuff

Description

This module includes everything you need to get started writing a parser.

By default this module is set up to parse character data. If you'd like to parse the result of your own tokenizer you should start with the following imports:

     import Text.Parsec.Prim
     import Text.Parsec.Combinator

Then you can implement your own version of `satisfy` on top of the `tokenPrim` primitive.

Synopsis

- data ParsecT s u m a
- type Parsec s u = ParsecT s u Identity
- token :: Stream s Identity t => (t -> String) -> (t -> SourcePos) -> (t -> Maybe a) -> Parsec s u a
- tokens :: (Stream s m t, Eq t) => ([t] -> String) -> (SourcePos -> [t] -> SourcePos) -> [t] -> ParsecT s u m [t]
- runParserT :: Stream s m t => ParsecT s u m a -> u -> SourceName -> s -> m (Either ParseError a)
- runParser :: Stream s Identity t => Parsec s u a -> u -> SourceName -> s -> Either ParseError a
- parse :: Stream s Identity t => Parsec s () a -> SourceName -> s -> Either ParseError a
- parseTest :: (Stream s Identity t, Show a) => Parsec s () a -> s -> IO ()
- getPosition :: Monad m => ParsecT s u m SourcePos
- getInput :: Monad m => ParsecT s u m s
- getState :: Monad m => ParsecT s u m u
- putState :: Monad m => u -> ParsecT s u m ()
- modifyState :: Monad m => (u -> u) -> ParsecT s u m ()
- (<|>) :: ParsecT s u m a -> ParsecT s u m a -> ParsecT s u m a
- (<?>) :: ParsecT s u m a -> String -> ParsecT s u m a
- label :: ParsecT s u m a -> String -> ParsecT s u m a
- labels :: ParsecT s u m a -> [String] -> ParsecT s u m a
- try :: ParsecT s u m a -> ParsecT s u m a
- unexpected :: Stream s m t => String -> ParsecT s u m a
- choice :: Stream s m t => [ParsecT s u m a] -> ParsecT s u m a
- many :: ParsecT s u m a -> ParsecT s u m [a]
- many1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m [a]
- skipMany :: ParsecT s u m a -> ParsecT s u m ()
- skipMany1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m ()
- count :: Stream s m t => Int -> ParsecT s u m a -> ParsecT s u m [a]
- between :: Stream s m t => ParsecT s u m open -> ParsecT s u m close -> ParsecT s u m a -> ParsecT s u m a
- option :: Stream s m t => a -> ParsecT s u m a -> ParsecT s u m a
- optionMaybe :: Stream s m t => ParsecT s u m a -> ParsecT s u m (Maybe a)
- optional :: Stream s m t => ParsecT s u m a -> ParsecT s u m ()
- sepBy :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a]
- sepBy1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a]
- endBy :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a]
- endBy1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a]
- sepEndBy :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a]
- sepEndBy1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a]
- chainl :: Stream s m t => ParsecT s u m a -> ParsecT s u m (a -> a -> a) -> a -> ParsecT s u m a
- chainl1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m (a -> a -> a) -> ParsecT s u m a
- chainr :: Stream s m t => ParsecT s u m a -> ParsecT s u m (a -> a -> a) -> a -> ParsecT s u m a
- chainr1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m (a -> a -> a) -> ParsecT s u m a
- eof :: (Stream s m t, Show t) => ParsecT s u m ()
- notFollowedBy :: (Stream s m t, Show a) => ParsecT s u m a -> ParsecT s u m ()
- manyTill :: Stream s m t => ParsecT s u m a -> ParsecT s u m end -> ParsecT s u m [a]
- lookAhead :: Stream s m t => ParsecT s u m a -> ParsecT s u m a
- anyToken :: (Stream s m t, Show t) => ParsecT s u m t
- module Text.Parsec.Char
- data ParseError
- errorPos :: ParseError -> SourcePos
- data SourcePos
- type SourceName = String
- type Line = Int
- type Column = Int
- sourceName :: SourcePos -> SourceName
- sourceLine :: SourcePos -> Line
- sourceColumn :: SourcePos -> Column
- incSourceLine :: SourcePos -> Line -> SourcePos
- incSourceColumn :: SourcePos -> Column -> SourcePos
- setSourceLine :: SourcePos -> Line -> SourcePos
- setSourceColumn :: SourcePos -> Column -> SourcePos
- setSourceName :: SourcePos -> SourceName -> SourcePos
- parserTrace :: (Show t, Stream s m t) => String -> ParsecT s u m ()
- parserTraced :: (Stream s m t, Show t) => String -> ParsecT s u m b -> ParsecT s u m b
- manyAccum :: (a -> [a] -> [a]) -> ParsecT s u m a -> ParsecT s u m [a]
- tokenPrim :: Stream s m t => (t -> String) -> (SourcePos -> t -> s -> SourcePos) -> (t -> Maybe a) -> ParsecT s u m a
- tokenPrimEx :: Stream s m t => (t -> String) -> (SourcePos -> t -> s -> SourcePos) -> Maybe (SourcePos -> t -> s -> u -> u) -> (t -> Maybe a) -> ParsecT s u m a
- runPT :: Stream s m t => ParsecT s u m a -> u -> SourceName -> s -> m (Either ParseError a)
- unknownError :: State s u -> ParseError
- sysUnExpectError :: String -> SourcePos -> Reply s u a
- mergeErrorReply :: ParseError -> Reply s u a -> Reply s u a
- getParserState :: Monad m => ParsecT s u m (State s u)
- setParserState :: Monad m => State s u -> ParsecT s u m (State s u)
- updateParserState :: (State s u -> State s u) -> ParsecT s u m (State s u)
- class Monad m => Stream s m t | s -> t where
  - uncons :: s -> m (Maybe (t, s))
- runParsecT :: Monad m => ParsecT s u m a -> State s u -> m (Consumed (m (Reply s u a)))
- mkPT :: Monad m => (State s u -> m (Consumed (m (Reply s u a)))) -> ParsecT s u m a
- runP :: Stream s Identity t => Parsec s u a -> u -> SourceName -> s -> Either ParseError a
- data Consumed a
  - = Consumed a
  - | Empty !a
- data Reply s u a
  - = Ok a !(State s u) ParseError
  - | Error ParseError
- data State s u = State {
  - stateInput :: s
  - statePos :: !SourcePos
  - stateUser :: !u
  }
- setPosition :: Monad m => SourcePos -> ParsecT s u m ()
- setInput :: Monad m => s -> ParsecT s u m ()
- setState :: Monad m => u -> ParsecT s u m ()
- updateState :: Monad m => (u -> u) -> ParsecT s u m ()
- parsecMap :: (a -> b) -> ParsecT s u m a -> ParsecT s u m b
- parserReturn :: a -> ParsecT s u m a
- parserBind :: ParsecT s u m a -> (a -> ParsecT s u m b) -> ParsecT s u m b
- parserFail :: String -> ParsecT s u m a
- parserZero :: ParsecT s u m a
- parserPlus :: ParsecT s u m a -> ParsecT s u m a -> ParsecT s u m a

# Parsers

data ParsecT s u m a #

ParserT monad transformer and Parser type

`ParsecT s u m a` is a parser with stream type `s`, user state type `u`, underlying monad `m` and return type `a`. Parsec is strict in the user state. If this is undesirable, simply use a data type like `data Box a = Box a` and the state type `Box YourStateType` to add a level of indirection.

Instances

MonadState s m => MonadState s (ParsecT s' u m) # |
Instance details Defined in Text.Parsec.Prim Methods get :: ParsecT s' u m s Source # put :: s -> ParsecT s' u m () Source # state :: (s -> (a, s)) -> ParsecT s' u m a Source #
MonadReader r m => MonadReader r (ParsecT s u m) # |
Instance details Defined in Text.Parsec.Prim Methods ask :: ParsecT s u m r Source # local :: (r -> r) -> ParsecT s u m a -> ParsecT s u m a Source # reader :: (r -> a) -> ParsecT s u m a Source #
MonadError e m => MonadError e (ParsecT s u m) # |
Instance details Defined in Text.Parsec.Prim Methods throwError :: e -> ParsecT s u m a Source # catchError :: ParsecT s u m a -> (e -> ParsecT s u m a) -> ParsecT s u m a Source #
MonadTrans (ParsecT s u) # |
Instance details Defined in Text.Parsec.Prim Methods lift :: Monad m => m a -> ParsecT s u m a
Monad (ParsecT s u m) # |
Instance details Defined in Text.Parsec.Prim Methods (>>=) :: ParsecT s u m a -> (a -> ParsecT s u m b) -> ParsecT s u m b Source # (>>) :: ParsecT s u m a -> ParsecT s u m b -> ParsecT s u m b Source # return :: a -> ParsecT s u m a Source # fail :: String -> ParsecT s u m a Source #
Functor (ParsecT s u m) # |
Instance details Defined in Text.Parsec.Prim Methods fmap :: (a -> b) -> ParsecT s u m a -> ParsecT s u m b Source # (<$) :: a -> ParsecT s u m b -> ParsecT s u m a Source #
MonadFail (ParsecT s u m) # | Since: parsec-3.1.12.0
Instance details Defined in Text.Parsec.Prim Methods fail :: String -> ParsecT s u m a Source #
Applicative (ParsecT s u m) # |
Instance details Defined in Text.Parsec.Prim Methods pure :: a -> ParsecT s u m a Source # (<*>) :: ParsecT s u m (a -> b) -> ParsecT s u m a -> ParsecT s u m b Source # liftA2 :: (a -> b -> c) -> ParsecT s u m a -> ParsecT s u m b -> ParsecT s u m c Source # (*>) :: ParsecT s u m a -> ParsecT s u m b -> ParsecT s u m b Source # (<*) :: ParsecT s u m a -> ParsecT s u m b -> ParsecT s u m a Source #
MonadIO m => MonadIO (ParsecT s u m) # |
Instance details Defined in Text.Parsec.Prim Methods liftIO :: IO a -> ParsecT s u m a Source #
Alternative (ParsecT s u m) # |
Instance details Defined in Text.Parsec.Prim Methods empty :: ParsecT s u m a Source # (<|>) :: ParsecT s u m a -> ParsecT s u m a -> ParsecT s u m a Source # some :: ParsecT s u m a -> ParsecT s u m [a] Source # many :: ParsecT s u m a -> ParsecT s u m [a] Source #
MonadPlus (ParsecT s u m) # |
Instance details Defined in Text.Parsec.Prim Methods mzero :: ParsecT s u m a Source # mplus :: ParsecT s u m a -> ParsecT s u m a -> ParsecT s u m a Source #
MonadCont m => MonadCont (ParsecT s u m) # |
Instance details Defined in Text.Parsec.Prim Methods callCC :: ((a -> ParsecT s u m b) -> ParsecT s u m a) -> ParsecT s u m a Source #
Semigroup a => Semigroup (ParsecT s u m a) # | The `Semigroup` instance for `ParsecT` is used to append the result of several parsers, for example:
    (many $ char a) <> (many $ char b)
The above will parse a string like `"aabbb"` and return a successful parse result `"aabbb"`. Compare against the below which will produce a result of `"bbb"` for the same input:
    (many $ char a) >> (many $ char b)
    (many $ char a) *> (many $ char b)
Since: parsec-3.1.12
Instance details Defined in Text.Parsec.Prim Methods (<>) :: ParsecT s u m a -> ParsecT s u m a -> ParsecT s u m a Source # sconcat :: NonEmpty (ParsecT s u m a) -> ParsecT s u m a Source # stimes :: Integral b => b -> ParsecT s u m a -> ParsecT s u m a Source #
(Monoid a, Semigroup (ParsecT s u m a)) => Monoid (ParsecT s u m a) # | The `Monoid` instance for `ParsecT` is used for the same purposes as the `Semigroup` instance. Since: parsec-3.1.12
Instance details Defined in Text.Parsec.Prim Methods mempty :: ParsecT s u m a Source # mappend :: ParsecT s u m a -> ParsecT s u m a -> ParsecT s u m a Source # mconcat :: [ParsecT s u m a] -> ParsecT s u m a Source #

type Parsec s u = ParsecT s u Identity #

token #

Arguments

:: Stream s Identity t |
=> (t -> String) | Token pretty-printing function.
-> (t -> SourcePos) | Computes the position of a token.
-> (t -> Maybe a) | Matching function for the token to parse.
-> Parsec s u a |

The parser `token showTok posFromTok testTok` accepts a token `t` with result `x` when the function `testTok t` returns ``Just` x`. The source position of the `t` should be returned by `posFromTok t` and the token can be shown using `showTok t`.

This combinator is expressed in terms of `tokenPrim`. It is used to accept user defined token streams. For example, suppose that we have a stream of basic tokens tupled with source positions. We can then define a parser that accepts single tokens as:

     mytoken x
       = token showTok posFromTok testTok
       where
         showTok (pos,t)     = show t
         posFromTok (pos,t)  = pos
         testTok (pos,t)     = if x == t then Just t else Nothing

tokens :: (Stream s m t, Eq t) => ([t] -> String) -> (SourcePos -> [t] -> SourcePos) -> [t] -> ParsecT s u m [t] #

runParserT :: Stream s m t => ParsecT s u m a -> u -> SourceName -> s -> m (Either ParseError a) #

The most general way to run a parser. `runParserT p state filePath input` runs parser `p` on the input list of tokens `input`, obtained from source `filePath` with the initial user state `st`. The `filePath` is only used in error messages and may be the empty string. Returns a computation in the underlying monad `m` that return either a `ParseError` (`Left`) or a value of type `a` (`Right`).

runParser :: Stream s Identity t => Parsec s u a -> u -> SourceName -> s -> Either ParseError a #

The most general way to run a parser over the Identity monad. `runParser p state filePath input` runs parser `p` on the input list of tokens `input`, obtained from source `filePath` with the initial user state `st`. The `filePath` is only used in error messages and may be the empty string. Returns either a `ParseError` (`Left`) or a value of type `a` (`Right`).

     parseFromFile p fname
       = do{ input <- readFile fname
           ; return (runParser p () fname input)
           }

parse :: Stream s Identity t => Parsec s () a -> SourceName -> s -> Either ParseError a #

`parse p filePath input` runs a parser `p` over Identity without user state. The `filePath` is only used in error messages and may be the empty string. Returns either a `ParseError` (`Left`) or a value of type `a` (`Right`).

     main    = case (parse numbers "" "11, 2, 43") of
                Left err  -> print err
                Right xs  -> print (sum xs)

     numbers = commaSep integer

parseTest :: (Stream s Identity t, Show a) => Parsec s () a -> s -> IO () #

The expression `parseTest p input` applies a parser `p` against input `input` and prints the result to stdout. Used for testing parsers.

getPosition :: Monad m => ParsecT s u m SourcePos #

Returns the current source position. See also `SourcePos`.

getInput :: Monad m => ParsecT s u m s #

Returns the current input

getState :: Monad m => ParsecT s u m u #

Returns the current user state.

putState :: Monad m => u -> ParsecT s u m () #

`putState st` set the user state to `st`.

modifyState :: Monad m => (u -> u) -> ParsecT s u m () #

`modifyState f` applies function `f` to the user state. Suppose that we want to count identifiers in a source, we could use the user state as:

     expr  = do{ x <- identifier
               ; modifyState (+1)
               ; return (Id x)
               }

# Combinators

(<|>) :: ParsecT s u m a -> ParsecT s u m a -> ParsecT s u m a infixr 1 #

This combinator implements choice. The parser `p <|> q` first applies `p`. If it succeeds, the value of `p` is returned. If `p` fails without consuming any input, parser `q` is tried. This combinator is defined equal to the `mplus` member of the `MonadPlus` class and the (`<|>`) member of `Alternative`.

The parser is called predictive since `q` is only tried when parser `p` didn't consume any input (i.e.. the look ahead is 1). This non-backtracking behaviour allows for both an efficient implementation of the parser combinators and the generation of good error messages.

(<?>) :: ParsecT s u m a -> String -> ParsecT s u m a infix 0 #

The parser `p <?> msg` behaves as parser `p`, but whenever the parser `p` fails without consuming any input, it replaces expect error messages with the expect error message `msg`.

This is normally used at the end of a set alternatives where we want to return an error message in terms of a higher level construct rather than returning all possible characters. For example, if the `expr` parser from the `try` example would fail, the error message is: '...: expecting expression'. Without the `(<?>)` combinator, the message would be like '...: expecting "let" or letter', which is less friendly.

label :: ParsecT s u m a -> String -> ParsecT s u m a #

A synonym for `<?>`, but as a function instead of an operator.

labels :: ParsecT s u m a -> [String] -> ParsecT s u m a #

try :: ParsecT s u m a -> ParsecT s u m a #

The parser `try p` behaves like parser `p`, except that it pretends that it hasn't consumed any input when an error occurs.

This combinator is used whenever arbitrary look ahead is needed. Since it pretends that it hasn't consumed any input when `p` fails, the (`<|>`) combinator will try its second alternative even when the first parser failed while consuming input.

The `try` combinator can for example be used to distinguish identifiers and reserved words. Both reserved words and identifiers are a sequence of letters. Whenever we expect a certain reserved word where we can also expect an identifier we have to use the `try` combinator. Suppose we write:

     expr        = letExpr <|> identifier <?> "expression"

     letExpr     = do{ string "let"; ... }
     identifier  = many1 letter

If the user writes "lexical", the parser fails with: `unexpected 'x', expecting 't' in "let"`. Indeed, since the (`<|>`) combinator only tries alternatives when the first alternative hasn't consumed input, the `identifier` parser is never tried (because the prefix "le" of the `string "let"` parser is already consumed). The right behaviour can be obtained by adding the `try` combinator:

     expr        = letExpr <|> identifier <?> "expression"

     letExpr     = do{ try (string "let"); ... }
     identifier  = many1 letter

unexpected :: Stream s m t => String -> ParsecT s u m a #

The parser `unexpected msg` always fails with an unexpected error message `msg` without consuming any input.

The parsers `fail`, (`<?>`) and `unexpected` are the three parsers used to generate error messages. Of these, only (`<?>`) is commonly used. For an example of the use of `unexpected`, see the definition of `notFollowedBy`.

choice :: Stream s m t => [ParsecT s u m a] -> ParsecT s u 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.

many :: ParsecT s u m a -> ParsecT s u m [a] #

`many p` applies the parser `p` zero or more times. Returns a list of the returned values of `p`.

     identifier  = do{ c  <- letter
                     ; cs <- many (alphaNum <|> char '_')
                     ; return (c:cs)
                     }

many1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m [a] #

`many1 p` applies the parser `p` one or more times. Returns a list of the returned values of `p`.

     word  = many1 letter

skipMany :: ParsecT s u m a -> ParsecT s u m () #

`skipMany p` applies the parser `p` zero or more times, skipping its result.

     spaces  = skipMany space

skipMany1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m () #

`skipMany1 p` applies the parser `p` one or more times, skipping its result.

count :: Stream s m t => Int -> ParsecT s u m a -> ParsecT s u 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`.

between :: Stream s m t => ParsecT s u m open -> ParsecT s u m close -> ParsecT s u m a -> ParsecT s u m a #

`between open close p` parses `open`, followed by `p` and `close`. Returns the value returned by `p`.

     braces  = between (symbol "{") (symbol "}")

option :: Stream s m t => a -> ParsecT s u m a -> ParsecT s u 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 (do{ d <- digit
                             ; return (digitToInt d)
                             })

optionMaybe :: Stream s m t => ParsecT s u m a -> ParsecT s u m (Maybe a) #

`optionMaybe p` tries to apply parser `p`. If `p` fails without consuming input, it return `Nothing`, otherwise it returns `Just` the value returned by `p`.

optional :: Stream s m t => ParsecT s u m a -> ParsecT s u m () #

`optional 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`.

sepBy :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u 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 :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a] #

`sepBy1 p sep` parses one or more occurrences of `p`, separated by `sep`. Returns a list of values returned by `p`.

endBy :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u 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

endBy1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u 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`.

sepEndBy :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u 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

sepEndBy1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u 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`.

chainl :: Stream s m t => ParsecT s u m a -> ParsecT s u m (a -> a -> a) -> a -> ParsecT s u 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.

chainl1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m (a -> a -> a) -> ParsecT s u m a #

`chainl1 p op` 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   =   do{ symbol "*"; return (*)   }
             <|> do{ symbol "/"; return (div) }

     addop   =   do{ symbol "+"; return (+) }
             <|> do{ symbol "-"; return (-) }

chainr :: Stream s m t => ParsecT s u m a -> ParsecT s u m (a -> a -> a) -> a -> ParsecT s u 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.

chainr1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m (a -> a -> a) -> ParsecT s u 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`.

eof :: (Stream s m t, Show t) => ParsecT s u 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 anyToken <?> "end of input"

notFollowedBy :: (Stream s m t, Show a) => ParsecT s u m a -> ParsecT s u 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 (do{ string "let"
                          ; notFollowedBy alphaNum
                          })

NOTE: Currently, `notFollowedBy` exhibits surprising behaviour when applied to a parser `p` that doesn't consume any input; specifically

- ``notFollowedBy` . `notFollowedBy`` is not equivalent to `lookAhead`, and
- ``notFollowedBy` `eof`` never fails.

See haskell/parsec#8 for more details.

manyTill :: Stream s m t => ParsecT s u m a -> ParsecT s u m end -> ParsecT s u 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.

lookAhead :: Stream s m t => ParsecT s u m a -> ParsecT s u m a #

`lookAhead p` parses `p` without consuming any input.

If `p` fails and consumes some input, so does `lookAhead`. Combine with `try` if this is undesirable.

anyToken :: (Stream s m t, Show t) => ParsecT s u m t #

The parser `anyToken` accepts any kind of token. It is for example used to implement `eof`. Returns the accepted token.

# Character Parsing

module Text.Parsec.Char

# Error messages

data ParseError #

The abstract data type `ParseError` represents parse errors. It provides the source position (`SourcePos`) of the error and a list of error messages (`Message`). A `ParseError` can be returned by the function `parse`. `ParseError` is an instance of the `Show` and `Eq` classes.

Instances

Eq ParseError # |
Instance details Defined in Text.Parsec.Error Methods (==) :: ParseError -> ParseError -> Bool # (/=) :: ParseError -> ParseError -> Bool #
Show ParseError # |
Instance details Defined in Text.Parsec.Error Methods showsPrec :: Int -> ParseError -> ShowS Source # show :: ParseError -> String Source # showList :: [ParseError] -> ShowS Source #

errorPos :: ParseError -> SourcePos #

Extracts the source position from the parse error

# Position

data SourcePos #

The abstract data type `SourcePos` represents source positions. It contains the name of the source (i.e. file name), a line number and a column number. `SourcePos` is an instance of the `Show`, `Eq` and `Ord` class.

Instances

Eq SourcePos # |
Instance details Defined in Text.Parsec.Pos Methods (==) :: SourcePos -> SourcePos -> Bool # (/=) :: SourcePos -> SourcePos -> Bool #
Data SourcePos # |
Instance details Defined in Text.Parsec.Pos Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> SourcePos -> c SourcePos Source # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c SourcePos Source # toConstr :: SourcePos -> Constr Source # dataTypeOf :: SourcePos -> DataType Source # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c SourcePos) Source # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c SourcePos) Source # gmapT :: (forall b. Data b => b -> b) -> SourcePos -> SourcePos Source # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> SourcePos -> r Source # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> SourcePos -> r Source # gmapQ :: (forall d. Data d => d -> u) -> SourcePos -> [u] Source # gmapQi :: Int -> (forall d. Data d => d -> u) -> SourcePos -> u Source # gmapM :: Monad m => (forall d. Data d => d -> m d) -> SourcePos -> m SourcePos Source # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> SourcePos -> m SourcePos Source # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> SourcePos -> m SourcePos Source #
Ord SourcePos # |
Instance details Defined in Text.Parsec.Pos Methods compare :: SourcePos -> SourcePos -> Ordering # (<) :: SourcePos -> SourcePos -> Bool # (<=) :: SourcePos -> SourcePos -> Bool # (>) :: SourcePos -> SourcePos -> Bool # (>=) :: SourcePos -> SourcePos -> Bool # max :: SourcePos -> SourcePos -> SourcePos # min :: SourcePos -> SourcePos -> SourcePos #
Show SourcePos # |
Instance details Defined in Text.Parsec.Pos Methods showsPrec :: Int -> SourcePos -> ShowS Source # show :: SourcePos -> String Source # showList :: [SourcePos] -> ShowS Source #

type SourceName = String #

type Line = Int #

type Column = Int #

sourceName :: SourcePos -> SourceName #

Extracts the name of the source from a source position.

sourceLine :: SourcePos -> Line #

Extracts the line number from a source position.

sourceColumn :: SourcePos -> Column #

Extracts the column number from a source position.

incSourceLine :: SourcePos -> Line -> SourcePos #

Increments the line number of a source position.

incSourceColumn :: SourcePos -> Column -> SourcePos #

Increments the column number of a source position.

setSourceLine :: SourcePos -> Line -> SourcePos #

Set the line number of a source position.

setSourceColumn :: SourcePos -> Column -> SourcePos #

Set the column number of a source position.

setSourceName :: SourcePos -> SourceName -> SourcePos #

Set the name of the source.

# Debugging

As a more comprehensive alternative for debugging Parsec parsers, there's also the parsec-free package.

parserTrace :: (Show t, Stream s m t) => String -> ParsecT s u m () #

`parserTrace label` is an impure function, implemented with Debug.Trace that prints to the console the remaining parser state at the time it is invoked. It is intended to be used for debugging parsers by inspecting their intermediate states.

    *> parseTest (oneOf "aeiou"  >> parserTrace "label") "atest"
    label: "test"
    ...

Since: parsec-3.1.12.0

parserTraced :: (Stream s m t, Show t) => String -> ParsecT s u m b -> ParsecT s u m b #

`parserTraced label p` is an impure function, implemented with Debug.Trace that prints to the console the remaining parser state at the time it is invoked. It then continues to apply parser `p`, and if `p` fails will indicate that the label has been backtracked. It is intended to be used for debugging parsers by inspecting their intermediate states.

    *>  parseTest (oneOf "aeiou"  >> parserTraced "label" (oneOf "nope")) "atest"
    label: "test"
    label backtracked
    parse error at (line 1, column 2):
    ...

Since: parsec-3.1.12.0

# Low-level operations

manyAccum :: (a -> [a] -> [a]) -> ParsecT s u m a -> ParsecT s u m [a] #

tokenPrim #

Arguments

:: Stream s m t |
=> (t -> String) | Token pretty-printing function.
-> (SourcePos -> t -> s -> SourcePos) | Next position calculating function.
-> (t -> Maybe a) | Matching function for the token to parse.
-> ParsecT s u m a |

The parser `tokenPrim showTok nextPos testTok` accepts a token `t` with result `x` when the function `testTok t` returns ``Just` x`. The token can be shown using `showTok t`. The position of the next token should be returned when `nextPos` is called with the current source position `pos`, the current token `t` and the rest of the tokens `toks`, `nextPos pos t toks`.

This is the most primitive combinator for accepting tokens. For example, the `char` parser could be implemented as:

     char c
       = tokenPrim showChar nextPos testChar
       where
         showChar x        = "'" ++ x ++ "'"
         testChar x        = if x == c then Just x else Nothing
         nextPos pos x xs  = updatePosChar pos x

tokenPrimEx :: Stream s m t => (t -> String) -> (SourcePos -> t -> s -> SourcePos) -> Maybe (SourcePos -> t -> s -> u -> u) -> (t -> Maybe a) -> ParsecT s u m a #

runPT :: Stream s m t => ParsecT s u m a -> u -> SourceName -> s -> m (Either ParseError a) #

unknownError :: State s u -> ParseError #

sysUnExpectError :: String -> SourcePos -> Reply s u a #

mergeErrorReply :: ParseError -> Reply s u a -> Reply s u a #

getParserState :: Monad m => ParsecT s u m (State s u) #

Returns the full parser state as a `State` record.

setParserState :: Monad m => State s u -> ParsecT s u m (State s u) #

`setParserState st` set the full parser state to `st`.

updateParserState :: (State s u -> State s u) -> ParsecT s u m (State s u) #

`updateParserState f` applies function `f` to the parser state.

class Monad m => Stream s m t | s -> t where #

An instance of `Stream` has stream type `s`, underlying monad `m` and token type `t` determined by the stream

Some rough guidelines for a "correct" instance of Stream:

- unfoldM uncons gives the [t] corresponding to the stream
- A `Stream` instance is responsible for maintaining the "position within the stream" in the stream state `s`. This is trivial unless you are using the monad in a non-trivial way.

Methods

uncons :: s -> m (Maybe (t, s)) #

Instances

Monad m => Stream ByteString m Char # |
Instance details Defined in Text.Parsec.Prim Methods uncons :: ByteString -> m (Maybe (Char, ByteString)) #
Monad m => Stream ByteString m Char # |
Instance details Defined in Text.Parsec.Prim Methods uncons :: ByteString -> m (Maybe (Char, ByteString)) #
Monad m => Stream Text m Char # |
Instance details Defined in Text.Parsec.Prim Methods uncons :: Text -> m (Maybe (Char, Text)) #
Monad m => Stream Text m Char # |
Instance details Defined in Text.Parsec.Prim Methods uncons :: Text -> m (Maybe (Char, Text)) #
Monad m => Stream [tok] m tok # |
Instance details Defined in Text.Parsec.Prim Methods uncons :: [tok] -> m (Maybe (tok, [tok])) #

runParsecT :: Monad m => ParsecT s u m a -> State s u -> m (Consumed (m (Reply s u a))) #

Low-level unpacking of the ParsecT type. To run your parser, please look to runPT, runP, runParserT, runParser and other such functions.

mkPT :: Monad m => (State s u -> m (Consumed (m (Reply s u a)))) -> ParsecT s u m a #

Low-level creation of the ParsecT type. You really shouldn't have to do this.

runP :: Stream s Identity t => Parsec s u a -> u -> SourceName -> s -> Either ParseError a #

data Consumed a #

Constructors

Consumed a |
Empty !a |

Instances

Functor Consumed # |
Instance details Defined in Text.Parsec.Prim Methods fmap :: (a -> b) -> Consumed a -> Consumed b Source # (<$) :: a -> Consumed b -> Consumed a Source #

data Reply s u a #

Constructors

Ok a !(State s u) ParseError |
Error ParseError |

Instances

Functor (Reply s u) # |
Instance details Defined in Text.Parsec.Prim Methods fmap :: (a -> b) -> Reply s u a -> Reply s u b Source # (<$) :: a -> Reply s u b -> Reply s u a Source #

data State s u #

Constructors

State |
Fields stateInput :: s statePos :: !SourcePos stateUser :: !u

setPosition :: Monad m => SourcePos -> ParsecT s u m () #

`setPosition pos` sets the current source position to `pos`.

setInput :: Monad m => s -> ParsecT s u m () #

`setInput input` continues parsing with `input`. The `getInput` and `setInput` functions can for example be used to deal with #include files.

# Other stuff

setState :: Monad m => u -> ParsecT s u m () #

An alias for putState for backwards compatibility.

updateState :: Monad m => (u -> u) -> ParsecT s u m () #

An alias for modifyState for backwards compatibility.

parsecMap :: (a -> b) -> ParsecT s u m a -> ParsecT s u m b #

parserReturn :: a -> ParsecT s u m a #

parserBind :: ParsecT s u m a -> (a -> ParsecT s u m b) -> ParsecT s u m b #

parserFail :: String -> ParsecT s u m a #

parserZero :: ParsecT s u m a #

`parserZero` always fails without consuming any input. `parserZero` is defined equal to the `mzero` member of the `MonadPlus` class and to the `empty` member of the `Alternative` class.

parserPlus :: ParsecT s u m a -> ParsecT s u m a -> ParsecT s u m a #