Text.Parsec.Prim

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 | derek.a.elkins@gmail.com
Stability | provisional
Portability | portable
Safe Haskell | Safe
Language | Haskell2010

Text.Parsec.Prim

Description

The primitive parser combinators.

Synopsis

- unknownError :: State s u -> ParseError
- sysUnExpectError :: String -> SourcePos -> Reply s u a
- unexpected :: Stream s m t => String -> ParsecT s u m a
- data ParsecT s u m a
- 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
- type Parsec s u = ParsecT s u Identity
- 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
  }
- 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
- mergeErrorReply :: ParseError -> Reply s u a -> Reply s u a
- 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
- (<?>) :: ParsecT s u m a -> String -> ParsecT s u m a
- (<|>) :: ParsecT s u m a -> ParsecT s u m a -> 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
- lookAhead :: Stream s m t => ParsecT s u m a -> ParsecT s u m a
- class Monad m => Stream s m t | s -> t where
  - uncons :: s -> m (Maybe (t, s))
- tokens :: (Stream s m t, Eq t) => ([t] -> String) -> (SourcePos -> [t] -> SourcePos) -> [t] -> ParsecT s u m [t]
- try :: ParsecT s u m a -> ParsecT s u m a
- token :: Stream s Identity t => (t -> String) -> (t -> SourcePos) -> (t -> Maybe a) -> Parsec s u 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
- many :: ParsecT s u m a -> ParsecT s u m [a]
- skipMany :: ParsecT s u m a -> ParsecT s u m ()
- manyAccum :: (a -> [a] -> [a]) -> ParsecT s u m a -> ParsecT s u m [a]
- runPT :: Stream s m t => ParsecT s u m a -> u -> SourceName -> s -> m (Either ParseError a)
- runP :: Stream s Identity t => Parsec s u a -> u -> SourceName -> s -> Either ParseError a
- 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
- setPosition :: Monad m => SourcePos -> ParsecT s u m ()
- setInput :: Monad m => s -> ParsecT s u m ()
- 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)
- 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 ()
- setState :: Monad m => u -> ParsecT s u m ()
- updateState :: Monad m => (u -> u) -> ParsecT s u m ()

# Documentation

unknownError :: State s u -> ParseError #

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

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`.

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 #

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.

type Parsec s u = ParsecT s u Identity #

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

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 #

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

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 #

(<?>) :: 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.

(<|>) :: 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.

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 #

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.

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])) #

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

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

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

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 #

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)
                     }

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

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

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

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

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

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.

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.

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)
               }

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.