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 | Haskell98 |

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.

- 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
- 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
- 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
- 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

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 used a data type like `data Box a = Box a`

and
the state type `Box YourStateType`

to add a level of indirection.

MonadError e m => MonadError e (ParsecT s u m) Source # | |

MonadReader r m => MonadReader r (ParsecT s u m) Source # | |

MonadState s m => MonadState s (ParsecT s' u m) Source # | |

MonadTrans (ParsecT s u) Source # | |

Monad (ParsecT s u m) Source # | |

Functor (ParsecT s u m) Source # | |

Applicative (ParsecT s u m) Source # | |

MonadIO m => MonadIO (ParsecT s u m) Source # | |

Alternative (ParsecT s u m) Source # | |

MonadPlus (ParsecT s u m) Source # | |

MonadCont m => MonadCont (ParsecT s u m) Source # | |

:: 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

. The
source position of the `Just`

x`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 than 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] Source #

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

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 Source #

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 Source #

`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 () Source #

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 Source #

Returns the current source position. See also `SourcePos`

.

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

`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 Source #

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 Source #

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 Source #

A synonym for `<?>`

, but as a function instead of an operator.

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

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 Source #

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 Source #

`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] Source #

`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] Source #

`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 () Source #

`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 () Source #

`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] Source #

`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 Source #

`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 Source #

`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) })

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

`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] Source #

`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] Source #

`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] Source #

`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] Source #

`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] Source #

`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] Source #

`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 Source #

`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 Source #

`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 = 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 Source #

`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 Source #

`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 () Source #

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 () Source #

`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 })

manyTill :: Stream s m t => ParsecT s u m a -> ParsecT s u m end -> ParsecT s u m [a] Source #

`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 Source #

`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 Source #

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 Source #

errorPos :: ParseError -> SourcePos Source #

Extracts the source position from the parse error

# Position

type SourceName = String Source #

sourceName :: SourcePos -> SourceName Source #

Extracts the name of the source from a source position.

sourceLine :: SourcePos -> Line Source #

Extracts the line number from a source position.

sourceColumn :: SourcePos -> Column Source #

Extracts the column number from a source position.

incSourceLine :: SourcePos -> Line -> SourcePos Source #

Increments the line number of a source position.

incSourceColumn :: SourcePos -> Column -> SourcePos Source #

Increments the column number of a source position.

setSourceColumn :: SourcePos -> Column -> SourcePos Source #

Set the column number of a source position.

setSourceName :: SourcePos -> SourceName -> SourcePos Source #

Set the name of the source.

# Low-level operations

:: 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

. The
token can be shown using `Just`

x`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 Source #

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

unknownError :: State s u -> ParseError Source #

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

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

Returns the full parser state as a `State`

record.

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

`setParserState st`

set the full parser state to `st`

.

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

`updateParserState f`

applies function `f`

to the parser state.

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

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.

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

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 Source #

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 Source #

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

`setPosition pos`

sets the current source position to `pos`

.

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

`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 () Source #

An alias for putState for backwards compatibility.

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

An alias for modifyState for backwards compatibility.

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

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

parserZero :: ParsecT s u m a Source #

`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.