- class (Functor p, Monad p) => PolyParse p where
- 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
- optional :: PolyParse p => p a -> p (Maybe a)
- exactly :: PolyParse p => Int -> p a -> p [a]
- many :: PolyParse p => 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]
The PolyParse class
PolyParse class is an abstraction over all the current
concrete representations of monadic 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.
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
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.
p applies the transformation
f to any error message
p, having no effect if
p means parse p, unless p fails, in which case
parse q instead.
Can be chained together to give multiple attempts to parse something.
(Note that q could itself be a failing parser, e.g. to change the error
message from that defined in p to something different.)
However, a severe failure in p cannot be ignored.
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.
Apply a parsed function to a parsed value. Rather like ordinary function application lifted into parsers.
Combinators general to all parser types.
x parses both x and y, but discards the result of y.
const lifted into parsers.
When a simple fail is not strong enough, use failBad for emphasis. An emphasised (severe) error cannot be overridden by choice operators.
adjustErrBad is just like
adjustErr except it also raises the
severity of the error.
Helper for formatting error messages: indents all lines by a fixed amount.
optional indicates whether the parser succeeded through the Maybe type.
'exactly n p' parses precisely n items, using the parser p, in sequence.
'many p' parses a list of elements with individual parser p. Cannot fail, since an empty list is a valid return value.
Parse a list of items separated by discarded junk.
Parse a non-empty list of items separated by discarded junk.
Parse a list of items, discarding the start, end, and separator items.
Parse a bracketed item, discarding the brackets.