Safe Haskell | Safe-Inferred |
---|---|

Language | Haskell98 |

- class Commitment p where
- class (Functor p, Monad p, Applicative p, Alternative p, Commitment p) => PolyParse p
- apply :: PolyParse p => p (a -> b) -> p a -> p b
- discard :: PolyParse p => p a -> p b -> p a
- failBad :: PolyParse p => String -> p a
- adjustErrBad :: PolyParse p => p a -> (String -> String) -> p a
- indent :: Int -> String -> String
- oneOf :: PolyParse p => [p a] -> p a
- exactly :: PolyParse p => Int -> p a -> p [a]
- upto :: PolyParse p => Int -> p a -> p [a]
- many1 :: PolyParse p => p a -> p [a]
- sepBy :: PolyParse p => p a -> p sep -> p [a]
- sepBy1 :: PolyParse p => p a -> p sep -> p [a]
- bracketSep :: PolyParse p => p bra -> p sep -> p ket -> p a -> p [a]
- bracket :: PolyParse p => p bra -> p ket -> p a -> p a
- manyFinally :: PolyParse p => p a -> p z -> p [a]
- manyFinally' :: (PolyParse p, Show a) => p a -> p z -> p [a]

# The PolyParse classes

class Commitment p where Source

The `Commitment`

class is an abstraction over all the current
concrete representations of monadic/applicative parser combinators in this
package. The common feature is two-level error-handling.
Some primitives must be implemented specific to each parser type
(e.g. depending on whether the parser has a running state, or
whether it is lazy). But given those primitives, large numbers of
combinators do not depend any further on the internal structure of
the particular parser.

Commit is a way of raising the severity of any errors found within its argument. Used in the middle of a parser definition, it means that any operations prior to commitment fail softly, but after commitment, they fail hard.

adjustErr :: p a -> (String -> String) -> p a Source

`p `

applies the transformation `adjustErr`

f`f`

to any error message
generated in `p`

, having no effect if `p`

succeeds.

oneOf' :: [(String, p a)] -> p a Source

Parse the first alternative that succeeds, but if none succeed, report only the severe errors, and if none of those, then report all the soft errors.

Commitment Parser | |

Commitment Parser | |

Commitment Parser | |

Commitment (Parser t) | |

Commitment (Parser t) | |

Commitment (Parser t) | |

Commitment (Parser s) | |

Commitment (Parser s t) | |

Commitment (Parser s t) |

class (Functor p, Monad p, Applicative p, Alternative p, Commitment p) => PolyParse p Source

The `PolyParse`

class is an abstraction gathering all of the common
features that a two-level error-handling parser requires:
the applicative parsing interface, the monadic interface, and commitment.

There are two additional basic combinators that we expect to be implemented
afresh for every concrete type, but which (for technical reasons)
cannot be class methods. They are `next`

and `satisfy`

.

# Combinators general to all parser types.

## Simple combinators

apply :: PolyParse p => p (a -> b) -> p a -> p b infixl 3 Source

Apply a parsed function to a parsed value. Rather like ordinary function application lifted into parsers.

discard :: PolyParse p => p a -> p b -> p a infixl 3 Source

`x `

parses both x and y, but discards the result of y.
Rather like `discard`

y`const`

lifted into parsers.

## Error-handling

failBad :: PolyParse p => String -> p a Source

When a simple fail is not strong enough, use failBad for emphasis. An emphasised (severe) error cannot be overridden by choice operators.

adjustErrBad :: PolyParse p => p a -> (String -> String) -> p a Source

`adjustErrBad`

is just like `adjustErr`

except it also raises the
severity of the error.

indent :: Int -> String -> String Source

Helper for formatting error messages: indents all lines by a fixed amount.

## Choices

## Sequences

exactly :: PolyParse p => Int -> p a -> p [a] Source

'exactly n p' parses precisely n items, using the parser p, in sequence.

upto :: PolyParse p => Int -> p a -> p [a] Source

'upto n p' parses n or fewer items, using the parser p, in sequence.

sepBy :: PolyParse p => p a -> p sep -> p [a] Source

Parse a list of items separated by discarded junk.

sepBy1 :: PolyParse p => p a -> p sep -> p [a] Source

Parse a non-empty list of items separated by discarded junk.

bracketSep :: PolyParse p => p bra -> p sep -> p ket -> p a -> p [a] Source

Parse a list of items, discarding the start, end, and separator items.

bracket :: PolyParse p => p bra -> p ket -> p a -> p a Source

Parse a bracketed item, discarding the brackets.
If everything matches *except* the closing bracket, the whole
parse fails soft, which can give less-than-satisfying error messages.
If you want better error messages, try calling with e.g.
`bracket open (commit close) item`

manyFinally :: PolyParse p => p a -> p z -> p [a] Source

`manyFinally e t`

parses a possibly-empty sequence of `e`

's,
terminated by a `t`

. The final `t`

is discarded. Any parse failures
could be due either to a badly-formed terminator or a badly-formed
element, so it raises both possible errors.

manyFinally' :: (PolyParse p, Show a) => p a -> p z -> p [a] Source

`manyFinally'`

is like `manyFinally`

, except when the terminator
parser overlaps with the element parser. In `manyFinally e t`

,
the parser `t`

is tried only when parser `e`

fails, whereas in
`manyFinally' e t`

, the parser `t`

is always tried first, then
parser `e`

only if the terminator is not found. For instance,
`manyFinally (accept "01") (accept "0")`

on input `"0101010"`

returns
`["01","01","01"]`

, whereas `manyFinally'`

with the same arguments
and input returns `[]`

.