Text.Parsec.Class

HasParser can be considered a dual to Pretty like Read is to Show. The class provides Data.Parsec parsers for its instances that construct the type from its textual representation. Combined with the parseM and parse convenience functions, this class makes parsing simple. Unlike Read, Parsec parsers return reasonable error messages in case of failure. Also, there is a rich set of combinators and additional libraries available for re-use.

Documentation

type CharParser st input m a = Stream st m Char => ParsecT st input m a

A simplified ParsecT parser that consumes some kind of character stream without requiring any particular state state.

class HasParser a where

Types that are instances of this class can be parsed and constructed from some character based text representation.

Methods

parser :: CharParser st input m a

Instances

HasParser Natural

Defined in Text.Parsec.Class

Methods

parser :: forall st input (m :: Type -> Type). CharParser st input m Natural

type ErrorContext = String

Parsers functions like parse or parseM use this type to provide a helpful context in case the parser failes. Parsec uses the synonym SourceName for the same purpose, but in fact this type doesn't necessarily have to be a file name. It can be any name or identifier. Oftentimes, it it's useful to pass the name of the type that the parser attempted to parse.

parseM :: (MonadFail m, Stream input m Char, HasParser a) => ErrorContext -> input -> m a

Convenience wrapper around runParserT that uses the HasParser class to determine the desired parser for the given result type. The function reports syntax errors via fail.

>>> parseM "Natural" "987654321" :: IO Natural
987654321
>>> parseM "Natural" "123456789" :: Maybe Natural
Just 123456789

Please note that parsers run this way do not ignore any white space:

>>> parseM "Natural" " 1" :: Maybe Natural
Nothing
>>> parseM "Natural" "1 " :: Maybe Natural
Nothing

parse :: (Stream input Identity Char, HasParser a) => ErrorContext -> input -> a

Convenience wrapper around runParser that uses the HasParser class to determine the desired parser for the given result type. The function reports syntax errors by throwing ParseError. This approach is inherently impure and complicates error handling greatly. Use this function only on occasions where parser errors are fatal errors that your code cannot recover from. In almost all cases, parseM is the better choice.

>>> parse "Natural" "12345" :: Natural
12345

Like parseM, this function does not skip over any white space. Use Parsec's primitive runParser or runParserT functions if you don't like this behavior:

>>> runParser (spaces >> parser) () "Natural" "  1  " :: Either ParseError Natural
Right 1

Re-exports from Text.Parsec

class Monad m => Stream s (m :: Type -> Type) 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

Defined in Text.Parsec.Prim

Methods

uncons :: ByteString -> m (Maybe (Char, ByteString))

Monad m => Stream ByteString m Char

Defined in Text.Parsec.Prim

Methods

uncons :: ByteString -> m (Maybe (Char, ByteString))

Monad m => Stream Text m Char

Defined in Text.Parsec.Prim

Methods

uncons :: Text -> m (Maybe (Char, Text))

Monad m => Stream Text m Char

Defined in Text.Parsec.Prim

Methods

uncons :: Text -> m (Maybe (Char, Text))

Monad m => Stream [tok] m tok

Defined in Text.Parsec.Prim

Methods

uncons :: [tok] -> m (Maybe (tok, [tok]))

data State s u

Constructors

State

Fields

• stateInput :: s
• statePos :: !SourcePos
• stateUser :: !u

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

Data SourcePos

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

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c SourcePos

toConstr :: SourcePos -> Constr

dataTypeOf :: SourcePos -> DataType

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c SourcePos)

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c SourcePos)

gmapT :: (forall b. Data b => b -> b) -> SourcePos -> SourcePos

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> SourcePos -> r

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> SourcePos -> r

gmapQ :: (forall d. Data d => d -> u) -> SourcePos -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> SourcePos -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> SourcePos -> m SourcePos

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> SourcePos -> m SourcePos

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> SourcePos -> m SourcePos

Show SourcePos

Defined in Text.Parsec.Pos

Methods

showsPrec :: Int -> SourcePos -> ShowS

show :: SourcePos -> String

showList :: [SourcePos] -> ShowS

Eq SourcePos

Defined in Text.Parsec.Pos

Methods

(==) :: SourcePos -> SourcePos -> Bool

(/=) :: SourcePos -> SourcePos -> Bool

Ord SourcePos

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

type Column = Int

type Line = Int

type SourceName = String

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

Exception ParseError

Defined in Text.Parsec.Class.Orphans

Methods

toException :: ParseError -> SomeException

fromException :: SomeException -> Maybe ParseError

displayException :: ParseError -> String

Show ParseError

Defined in Text.Parsec.Error

Methods

showsPrec :: Int -> ParseError -> ShowS

show :: ParseError -> String

showList :: [ParseError] -> ShowS

Eq ParseError

Defined in Text.Parsec.Error

Methods

(==) :: ParseError -> ParseError -> Bool

(/=) :: ParseError -> ParseError -> Bool

data Reply s u a

Constructors

Ok a !(State s u) ParseError

Error ParseError

Instances

Functor (Reply s u)

Defined in Text.Parsec.Prim

Methods

fmap :: (a -> b) -> Reply s u a -> Reply s u b

(<$) :: a -> Reply s u b -> Reply s u a

data Consumed a

Constructors

Consumed a

Empty !a

Instances

Functor Consumed

Defined in Text.Parsec.Prim

Methods

fmap :: (a -> b) -> Consumed a -> Consumed b

(<$) :: a -> Consumed b -> Consumed a

type Parsec s u = ParsecT s u Identity

data ParsecT s u (m :: Type -> Type) 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

MonadError e m => MonadError e (ParsecT s u m)

Defined in Text.Parsec.Prim

Methods

throwError :: e -> ParsecT s u m a

catchError :: ParsecT s u m a -> (e -> ParsecT s u m a) -> ParsecT s u m a

MonadReader r m => MonadReader r (ParsecT s u m)

Defined in Text.Parsec.Prim

Methods

ask :: ParsecT s u m r

local :: (r -> r) -> ParsecT s u m a -> ParsecT s u m a

reader :: (r -> a) -> ParsecT s u m a

MonadState s m => MonadState s (ParsecT s' u m)

Defined in Text.Parsec.Prim

Methods

get :: ParsecT s' u m s

put :: s -> ParsecT s' u m ()

state :: (s -> (a, s)) -> ParsecT s' u m a

MonadTrans (ParsecT s u)

Defined in Text.Parsec.Prim

Methods

lift :: Monad m => m a -> ParsecT s u m a

MonadFail (ParsecT s u m)

Since: parsec-3.1.12.0

Defined in Text.Parsec.Prim

Methods

fail :: String -> ParsecT s u m a

MonadIO m => MonadIO (ParsecT s u m)

Defined in Text.Parsec.Prim

Methods

liftIO :: IO a -> ParsecT s u m a

Alternative (ParsecT s u m)

Defined in Text.Parsec.Prim

Methods

empty :: ParsecT s u m a

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

some :: ParsecT s u m a -> ParsecT s u m [a]

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

Applicative (ParsecT s u m)

Defined in Text.Parsec.Prim

Methods

pure :: a -> ParsecT s u m a

(<*>) :: ParsecT s u m (a -> b) -> ParsecT s u m a -> ParsecT s u m b

liftA2 :: (a -> b -> c) -> ParsecT s u m a -> ParsecT s u m b -> ParsecT s u m c

(*>) :: ParsecT s u m a -> ParsecT s u m b -> ParsecT s u m b

(<*) :: ParsecT s u m a -> ParsecT s u m b -> ParsecT s u m a

Functor (ParsecT s u m)

Defined in Text.Parsec.Prim

Methods

fmap :: (a -> b) -> ParsecT s u m a -> ParsecT s u m b

(<$) :: a -> ParsecT s u m b -> ParsecT s u m a

Monad (ParsecT s u m)

Defined in Text.Parsec.Prim

Methods

(>>=) :: ParsecT s u m a -> (a -> ParsecT s u m b) -> ParsecT s u m b

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

return :: a -> ParsecT s u m a

MonadPlus (ParsecT s u m)

Defined in Text.Parsec.Prim

Methods

mzero :: ParsecT s u m a

mplus :: ParsecT s u m a -> ParsecT s u m a -> ParsecT s u m a

MonadCont m => MonadCont (ParsecT s u m)

Defined in Text.Parsec.Prim

Methods

callCC :: ((a -> ParsecT s u m b) -> ParsecT s u m a) -> ParsecT s u m a

(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

Defined in Text.Parsec.Prim

Methods

mempty :: ParsecT s u m a

mappend :: ParsecT s u m a -> ParsecT s u m a -> ParsecT s u m a

mconcat :: [ParsecT s u m a] -> ParsecT s u m a

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

Defined in Text.Parsec.Prim

Methods

(<>) :: ParsecT s u m a -> ParsecT s u m a -> ParsecT s u m a

sconcat :: NonEmpty (ParsecT s u m a) -> ParsecT s u m a

stimes :: Integral b => b -> ParsecT s u m a -> ParsecT s u m a

try :: forall s u (m :: Type -> Type) a. 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

(<|>) :: forall s u (m :: Type -> Type) a. 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.

many :: forall s u (m :: Type -> Type) a. 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)
                 }

satisfy :: forall s (m :: Type -> Type) u. Stream s m Char => (Char -> Bool) -> ParsecT s u m Char

The parser satisfy f succeeds for any character for which the supplied function f returns True. Returns the character that is actually parsed.

char :: forall s (m :: Type -> Type) u. Stream s m Char => Char -> ParsecT s u m Char

char c parses a single character c. Returns the parsed character (i.e. c).

 semiColon  = char ';'

eof :: forall s (m :: Type -> Type) t u. (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"

string :: forall s (m :: Type -> Type) u. Stream s m Char => String -> ParsecT s u m String

string s parses a sequence of characters given by s. Returns the parsed string (i.e. s).

 divOrMod    =   string "div"
             <|> string "mod"

Consider using string'.

choice :: forall s (m :: Type -> Type) t u a. 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.

count :: forall s (m :: Type -> Type) t u a. 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 :: forall s (m :: Type -> Type) t u open close a. 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 :: forall s (m :: Type -> Type) t a u. 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)
                         })

optional :: forall s (m :: Type -> Type) t u a. 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.

many1 :: forall s (m :: Type -> Type) t u a. 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 :: forall s u (m :: Type -> Type) a. 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 :: forall s (m :: Type -> Type) t u a. 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.

sepBy :: forall s (m :: Type -> Type) t u a sep. 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 :: forall s (m :: Type -> Type) t u a sep. 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 :: forall s (m :: Type -> Type) t u a sep. 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 :: forall s (m :: Type -> Type) t u a sep. 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.

chainr :: forall s (m :: Type -> Type) t u a. 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.

chainl :: forall s (m :: Type -> Type) t u a. 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.

chainr1 :: forall s (m :: Type -> Type) t u a. 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.

chainl1 :: forall s (m :: Type -> Type) t u a. 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 (-) }

manyTill :: forall s (m :: Type -> Type) t u a end. 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.

getState :: forall (m :: Type -> Type) s u. Monad m => ParsecT s u m u

Returns the current user state.

setState :: forall (m :: Type -> Type) u s. Monad m => u -> ParsecT s u m ()

An alias for putState for backwards compatibility.

sourceLine :: SourcePos -> Line

Extracts the line number from a source position.

sourceColumn :: SourcePos -> Column

Extracts the column number from a source position.

label :: forall s u (m :: Type -> Type) a. ParsecT s u m a -> String -> ParsecT s u m a

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

lookAhead :: forall s (m :: Type -> Type) t u a. 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.

unexpected :: forall s (m :: Type -> Type) t u a. 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.

(<?>) :: forall s u (m :: Type -> Type) 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.

notFollowedBy :: forall s (m :: Type -> Type) t a u. (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.

sourceName :: SourcePos -> SourceName

Extracts the name of the source 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.

setSourceName :: SourcePos -> SourceName -> SourcePos

Set the name of the source.

setSourceLine :: SourcePos -> Line -> SourcePos

Set the line number of a source position.

setSourceColumn :: SourcePos -> Column -> SourcePos

Set the column number of a source position.

errorPos :: ParseError -> SourcePos

Extracts the source position from the parse error

unknownError :: State s u -> ParseError

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

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.

parsecMap :: forall a b s u (m :: Type -> Type). (a -> b) -> ParsecT s u m a -> ParsecT s u m b

parserReturn :: forall a s u (m :: Type -> Type). a -> ParsecT s u m a

parserBind :: forall s u (m :: Type -> Type) a b. 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 :: forall s u (m :: Type -> Type) a. String -> ParsecT s u m a

parserZero :: forall s u (m :: Type -> Type) a. 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 :: forall s u (m :: Type -> Type) a. ParsecT s u m a -> ParsecT s u m a -> ParsecT s u m a

labels :: forall s u (m :: Type -> Type) a. ParsecT s u m a -> [String] -> ParsecT s u m a

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

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

:: forall s (m :: Type -> Type) t a u. 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 :: forall s (m :: Type -> Type) t u a. Stream s m t => (t -> String) -> (SourcePos -> t -> s -> SourcePos) -> Maybe (SourcePos -> t -> s -> u -> u) -> (t -> Maybe a) -> ParsecT s u m a

manyAccum :: forall a s u (m :: Type -> Type). (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)
       }

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 :: forall (m :: Type -> Type) s u. Monad m => ParsecT s u m SourcePos

Returns the current source position. See also SourcePos.

getInput :: forall (m :: Type -> Type) s u. Monad m => ParsecT s u m s

Returns the current input

setPosition :: forall (m :: Type -> Type) s u. Monad m => SourcePos -> ParsecT s u m ()

setPosition pos sets the current source position to pos.

setInput :: forall (m :: Type -> Type) s u. 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 :: forall (m :: Type -> Type) s u. Monad m => ParsecT s u m (State s u)

Returns the full parser state as a State record.

setParserState :: forall (m :: Type -> Type) s u. Monad m => State s u -> ParsecT s u m (State s u)

setParserState st set the full parser state to st.

updateParserState :: forall s u (m :: Type -> Type). (State s u -> State s u) -> ParsecT s u m (State s u)

updateParserState f applies function f to the parser state.

putState :: forall (m :: Type -> Type) u s. Monad m => u -> ParsecT s u m ()

putState st set the user state to st.

modifyState :: forall (m :: Type -> Type) u s. 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)
           }

updateState :: forall (m :: Type -> Type) u s. Monad m => (u -> u) -> ParsecT s u m ()

An alias for modifyState for backwards compatibility.

optionMaybe :: forall s (m :: Type -> Type) t u a. 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.

sepEndBy1 :: forall s (m :: Type -> Type) t u a sep. 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.

sepEndBy :: forall s (m :: Type -> Type) t u a sep. 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

anyToken :: forall s (m :: Type -> Type) t u. (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.

parserTrace :: forall t s (m :: Type -> Type) u. (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 :: forall s (m :: Type -> Type) t u b. (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

oneOf :: forall s (m :: Type -> Type) u. Stream s m Char => [Char] -> ParsecT s u m Char

oneOf cs succeeds if the current character is in the supplied list of characters cs. Returns the parsed character. See also satisfy.

  vowel  = oneOf "aeiou"

noneOf :: forall s (m :: Type -> Type) u. Stream s m Char => [Char] -> ParsecT s u m Char

As the dual of oneOf, noneOf cs succeeds if the current character not in the supplied list of characters cs. Returns the parsed character.

 consonant = noneOf "aeiou"

spaces :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m ()

Skips zero or more white space characters. See also skipMany.

space :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

Parses a white space character (any character which satisfies isSpace) Returns the parsed character.

newline :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

Parses a newline character ('\n'). Returns a newline character.

crlf :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

Parses a carriage return character ('\r') followed by a newline character ('\n'). Returns a newline character.

endOfLine :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

Parses a CRLF (see crlf) or LF (see newline) end-of-line. Returns a newline character ('\n').

endOfLine = newline <|> crlf

tab :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

Parses a tab character ('\t'). Returns a tab character.

upper :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

Parses an upper case letter (according to isUpper). Returns the parsed character.

lower :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

Parses a lower case character (according to isLower). Returns the parsed character.

alphaNum :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

Parses a alphabetic or numeric Unicode characters according to isAlphaNum. Returns the parsed character.

Note that numeric digits outside the ASCII range (such as arabic-indic digits like e.g. "٤" or U+0664), as well as numeric characters which aren't digits, are parsed by this function but not by digit.

letter :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

Parses an alphabetic Unicode characters (lower-case, upper-case and title-case letters, plus letters of caseless scripts and modifiers letters according to isAlpha). Returns the parsed character.

digit :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

Parses an ASCII digit. Returns the parsed character.

hexDigit :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

Parses a hexadecimal digit (a digit or a letter between 'a' and 'f' or 'A' and 'F'). Returns the parsed character.

octDigit :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

Parses an octal digit (a character between '0' and '7'). Returns the parsed character.

anyChar :: forall s (m :: Type -> Type) u. Stream s m Char => ParsecT s u m Char

This parser succeeds for any character. Returns the parsed character.

string' :: forall s (m :: Type -> Type) u. Stream s m Char => String -> ParsecT s u m String

string' s parses a sequence of characters given by s. Doesn't consume matching prefix.

 carOrCdr    =   string' "car"
             <|> string' "cdr"

Since: parsec-3.1.16.0