Text.Megaparsec.Combinator

Commonly used generic combinators. Note that all combinators works with any Alternative instances.

Documentation

between :: Applicative m => m open -> m close -> m a -> m a

between open close p parses open, followed by p and close. Returns the value returned by p.

braces = between (symbol "{") (symbol "}")

choice :: (Foldable f, Alternative m) => f (m a) -> 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 :: Alternative m => Int -> m a -> 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.

This parser is defined in terms of count', like this:

count n = count' n n

count' :: Alternative m => Int -> Int -> m a -> m [a]

count' m n p parses from m to n occurrences of p. If n is not positive or m > n, the parser equals to return []. Returns a list of parsed values.

Please note that m may be negative, in this case effect is the same as if it were equal to zero.

endBy :: Alternative m => m a -> m sep -> 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` semicolon

endBy1 :: Alternative m => m a -> m sep -> 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.

manyTill :: Alternative m => m a -> m end -> 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 = string "<!--" >> manyTill anyChar (try $ string "-->")

Note that we need to use try since parsers anyChar and string "-->" overlap and string "-->" could consume input before failing.

someTill :: Alternative m => m a -> m end -> m [a]

someTill p end works similarly to manyTill p end, but p should succeed at least once.

option :: Alternative m => a -> m a -> 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 (digitToInt <$> digitChar)

sepBy :: Alternative m => m a -> m sep -> 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` comma

sepBy1 :: Alternative m => m a -> m sep -> m [a]

sepBy1 p sep parses one or more occurrences of p, separated by sep. Returns a list of values returned by p.

skipMany :: Alternative m => m a -> m ()

skipMany p applies the parser p zero or more times, skipping its result.

space = skipMany spaceChar

skipSome :: Alternative m => m a -> m ()

skipSome p applies the parser p one or more times, skipping its result.

chainl :: Alternative m => m a -> m (a -> a -> a) -> a -> m a

Deprecated: Use Text.Megaparsec.Expr instead.

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 :: Alternative m => m a -> m (a -> a -> a) -> m a

Deprecated: Use Text.Megaparsec.Expr instead.

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.

Consider using Text.Megaparsec.Expr instead.

chainr :: Alternative m => m a -> m (a -> a -> a) -> a -> m a

Deprecated: Use Text.Megaparsec.Expr instead.

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.

Consider using Text.Megaparsec.Expr instead.

chainr1 :: Alternative m => m a -> m (a -> a -> a) -> m a

Deprecated: Use Text.Megaparsec.Expr instead.

chainr1 p op 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.

Consider using Text.Megaparsec.Expr instead.

sepEndBy :: Alternative m => m a -> m sep -> m [a]

Deprecated: Use sepBy p sep <* optional sep instead.

sepEndBy p sep parses zero or more occurrences of p, separated and optionally ended by sep. Returns a list of values returned by p.

sepEndBy1 :: Alternative m => m a -> m sep -> m [a]

Deprecated: Use sepBy1 p sep <* optional sep instead.

sepEndBy1 p sep parses one or more occurrences of p, separated and optionally ended by sep. Returns a list of values returned by p.