Copyright | (c) Daan Leijen 1999-2001 |
---|---|
License | BSD-style (see the file LICENSE) |
Maintainer | Christian Maeder <chr.maeder@web.de> |
Stability | provisional |
Portability | portable |
Safe Haskell | Safe-Inferred |
Language | Haskell98 |
Commonly used generic combinators
Synopsis
- between :: GenParser tok st open -> GenParser tok st close -> GenParser tok st a -> GenParser tok st a
- chainl :: GenParser tok st a -> GenParser tok st (a -> a -> a) -> a -> GenParser tok st a
- chainl1 :: GenParser tok st a -> GenParser tok st (a -> a -> a) -> GenParser tok st a
- chainr :: GenParser tok st a -> GenParser tok st (a -> a -> a) -> a -> GenParser tok st a
- chainr1 :: GenParser tok st a -> GenParser tok st (a -> a -> a) -> GenParser tok st a
- choice :: [GenParser tok st a] -> GenParser tok st a
- count :: Int -> GenParser tok st a -> GenParser tok st [a]
- endBy :: GenParser tok st a -> GenParser tok st sep -> GenParser tok st [a]
- endBy1 :: GenParser tok st a -> GenParser tok st sep -> GenParser tok st [a]
- eof :: Show tok => GenParser tok st ()
- many1 :: GenParser tok st a -> GenParser tok st [a]
- notFollowedBy :: Show a => GenParser tok st a -> GenParser tok st ()
- option :: a -> GenParser tok st a -> GenParser tok st a
- optionMaybe :: GenParser tok st a -> GenParser tok st (Maybe a)
- optional :: GenParser tok st a -> GenParser tok st ()
- sepBy :: GenParser tok st a -> GenParser tok st sep -> GenParser tok st [a]
- sepBy1 :: GenParser tok st a -> GenParser tok st sep -> GenParser tok st [a]
- sepEndBy :: GenParser tok st a -> GenParser tok st sep -> GenParser tok st [a]
- sepEndBy1 :: GenParser tok st a -> GenParser tok st sep -> GenParser tok st [a]
- skipMany1 :: GenParser tok st a -> GenParser tok st ()
- anyToken :: Show tok => GenParser tok st tok
- lookAhead :: GenParser tok st a -> GenParser tok st a
- manyTill :: GenParser tok st a -> GenParser tok st end -> GenParser tok st [a]
Documentation
between :: GenParser tok st open -> GenParser tok st close -> GenParser tok st a -> GenParser tok st a Source #
between open close p
parses open
, followed by p
and close
.
Returns the value returned by p
.
braces = between (symbol "{") (symbol "}")
chainl :: GenParser tok st a -> GenParser tok st (a -> a -> a) -> a -> GenParser tok st a Source #
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 :: GenParser tok st a -> GenParser tok st (a -> a -> a) -> GenParser tok st a Source #
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 = symbol "*" *> return (*) <|> symbol "/" *> return (div) addop = symbol "+" *> return (+) <|> symbol "-" *> return (-)
chainr :: GenParser tok st a -> GenParser tok st (a -> a -> a) -> a -> GenParser tok st a Source #
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 :: GenParser tok st a -> GenParser tok st (a -> a -> a) -> GenParser tok st a Source #
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
.
choice :: [GenParser tok st a] -> GenParser tok st 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.
count :: Int -> GenParser tok st a -> GenParser tok st [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
.
endBy :: GenParser tok st a -> GenParser tok st sep -> GenParser tok st [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 :: GenParser tok st a -> GenParser tok st sep -> GenParser tok st [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
.
eof :: Show tok => GenParser tok st () 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"
many1 :: GenParser tok st a -> GenParser tok st [a] Source #
many1 p
applies the parser p
one or more times. Returns a
list of the returned values of p
.
word = many1 letter
notFollowedBy :: Show a => GenParser tok st a -> GenParser tok st () 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 (string "let" <* notFollowedBy alphaNum)
option :: a -> GenParser tok st a -> GenParser tok st 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 (digitToInt <$> digit)
optional :: GenParser tok st a -> GenParser tok st () 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 :: GenParser tok st a -> GenParser tok st sep -> GenParser tok st [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 :: GenParser tok st a -> GenParser tok st sep -> GenParser tok st [a] Source #
sepBy1 p sep
parses one or more occurrences of p
, separated
by sep
. Returns a list of values returned by p
.
sepEndBy :: GenParser tok st a -> GenParser tok st sep -> GenParser tok st [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 :: GenParser tok st a -> GenParser tok st sep -> GenParser tok st [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
.
skipMany1 :: GenParser tok st a -> GenParser tok st () Source #
skipMany1 p
applies the parser p
one or more times, skipping
its result.
anyToken :: Show tok => GenParser tok st tok Source #
The parser anyToken
accepts any kind of token. It is for example
used to implement eof
. Returns the accepted token.
lookAhead :: GenParser tok st a -> GenParser tok st a Source #
lookAhead p
parses p
without consuming any input.
manyTill :: GenParser tok st a -> GenParser tok st end -> GenParser tok st [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 = string "<!--" *> manyTill anyChar (try (string "-->"))
Note the overlapping parsers anyChar
and string "-->"
, and
therefore the use of the try
combinator.