Copyright | © 2015–2016 Megaparsec contributors © 2007 Paolo Martini © 1999–2001 Daan Leijen |
---|---|

License | FreeBSD |

Maintainer | Mark Karpov <markkarpov@opmbx.org> |

Stability | experimental |

Portability | portable |

Safe Haskell | None |

Language | Haskell2010 |

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

instances.

- between :: Applicative m => m open -> m close -> m a -> m a
- choice :: (Foldable f, Alternative m) => f (m a) -> m a
- count :: Applicative m => Int -> m a -> m [a]
- count' :: Alternative m => Int -> Int -> m a -> m [a]
- eitherP :: Alternative m => m a -> m b -> m (Either a b)
- endBy :: Alternative m => m a -> m sep -> m [a]
- endBy1 :: Alternative m => m a -> m sep -> m [a]
- manyTill :: Alternative m => m a -> m end -> m [a]
- someTill :: Alternative m => m a -> m end -> m [a]
- option :: Alternative m => a -> m a -> m a
- sepBy :: Alternative m => m a -> m sep -> m [a]
- sepBy1 :: Alternative m => m a -> m sep -> m [a]
- sepEndBy :: Alternative m => m a -> m sep -> m [a]
- sepEndBy1 :: Alternative m => m a -> m sep -> m [a]
- skipMany :: Alternative m => m a -> m ()
- skipSome :: Alternative m => m a -> m ()

# Documentation

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

`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 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 :: Applicative m => Int -> m a -> 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.

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

`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.

eitherP :: Alternative m => m a -> m b -> m (Either a b) Source

Combine two alternatives.

*Since: 4.4.0*

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

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

.

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

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

`someTill p end`

works similarly to `manyTill p end`

, but `p`

should
succeed at least once.

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

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

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

`sepBy1 p sep`

parses *one* or more occurrences of `p`

, separated
by `sep`

. Returns a list of values returned by `p`

.

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

`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] 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`

.

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

`skipMany p`

applies the parser `p`

*zero* or more times, skipping
its result.

space = skipMany spaceChar

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

`skipSome p`

applies the parser `p`

*one* or more times, skipping
its result.