Portability | portable |
---|---|
Stability | provisional |
Maintainer | derek.a.elkins@gmail.com |
Safe Haskell | Safe-Infered |
Commonly used generic combinators
- choice :: Stream s m t => [ParsecT s u m a] -> ParsecT s u m a
- 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 ()
- skipMany1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m ()
- many1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m [a]
- 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
Documentation
choice :: Stream s m t => [ParsecT s u m a] -> ParsecT s u m aSource
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 :: 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 aSource
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 aSource
option x p
tries to apply parser p
. If p
fails without
consuming input, it returns the value x
, otherwise the value
returned by p
.
priority = option 0 (do{ d <- digit ; return (digitToInt d) })
optionMaybe :: Stream s m t => ParsecT s u m a -> ParsecT s u m (Maybe a)Source
optionMaybe p
tries to apply parser p
. If p
fails without
consuming input, it return Nothing
, otherwise it returns
Just
the value returned by p
.
optional :: Stream s m t => ParsecT s u m a -> ParsecT s u m ()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
.
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.
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
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
, seperated
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
, seperated
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 aSource
chainl p op x
parser 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 aSource
chainl1 p op x
parser 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 aSource
chainr p op x
parser 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 aSource
chainr1 p op x
parser 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.