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 |
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
- 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 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) Source # | |
MonadReader r m => MonadReader r (ParsecT s u m) Source # | |
MonadError e m => MonadError e (ParsecT s u m) Source # | |
throwError :: e -> ParsecT s u m a # catchError :: ParsecT s u m a -> (e -> ParsecT s u m a) -> ParsecT s u m a # | |
MonadTrans (ParsecT s u) Source # | |
Monad (ParsecT s u m) Source # | |
Functor (ParsecT s u m) Source # | |
MonadFail (ParsecT s u m) Source # | Since: 3.1.12.0 |
Applicative (ParsecT s u m) Source # | |
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 # | |
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 # | |
Semigroup a => Semigroup (ParsecT s u m a) Source # | The (many $ char The above will parse a string like (many $ char Since: 3.1.12 |
(Monoid a, Semigroup (ParsecT s u m a)) => Monoid (ParsecT s u m a) Source # | The Since: 3.1.12 |
:: 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
xt
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] 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
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 })
NOTE: Currently, notFollowedBy
exhibits surprising behaviour
when applied to a parser p
that doesn't consume any input;
specifically
is not equivalent tonotFollowedBy
.notFollowedBy
lookAhead
, and
never fails.notFollowedBy
eof
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] 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 #
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 Source # | |
(==) :: ParseError -> ParseError -> Bool # (/=) :: ParseError -> ParseError -> Bool # | |
Show ParseError Source # | |
showsPrec :: Int -> ParseError -> ShowS # show :: ParseError -> String # showList :: [ParseError] -> ShowS # |
errorPos :: ParseError -> SourcePos Source #
Extracts the source position from the parse error
Position
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 Source # | |
Data SourcePos Source # | |
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 :: (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 # | |
Ord SourcePos Source # | |
Show SourcePos Source # | |
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.
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 () Source #
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: 3.1.12.0
parserTraced :: (Stream s m t, Show t) => String -> ParsecT s u m b -> ParsecT s u m b Source #
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: 3.1.12.0
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
xshowTok 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 states
. This is trivial unless you are using the monad in a non-trivial way.
Instances
Monad m => Stream ByteString m Char Source # | |
uncons :: ByteString -> m (Maybe (Char, ByteString)) Source # | |
Monad m => Stream ByteString m Char Source # | |
uncons :: ByteString -> m (Maybe (Char, ByteString)) Source # | |
Monad m => Stream Text m Char Source # | |
Monad m => Stream Text m Char Source # | |
Monad m => Stream [tok] m tok Source # | |
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 #
Ok a !(State s u) ParseError | |
Error ParseError |
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.