| Safe Haskell | Safe-Infered |
|---|
Text.ParserCombinators.Poly.ByteString
Contents
- newtype Parser a = P (ByteString -> Result ByteString a)
- data Result z a
- runParser :: Parser a -> ByteString -> (Either String a, ByteString)
- next :: Parser Word8
- eof :: Parser ()
- satisfy :: (Word8 -> Bool) -> Parser Word8
- onFail :: Parser a -> Parser a -> Parser a
- manySatisfy :: (Word8 -> Bool) -> Parser ByteString
- many1Satisfy :: (Word8 -> Bool) -> Parser ByteString
- reparse :: ByteString -> Parser ()
- module Text.ParserCombinators.Poly.Base
The Parser datatype
This Parser datatype is a specialised parsing monad with error
reporting. Whereas the standard version can be used for arbitrary
token types, this version is specialised to ByteString input only.
Constructors
| P (ByteString -> Result ByteString a) |
A return type like Either, that distinguishes not only between right and wrong answers, but also has commitment, so that a failure cannot be undone. This should only be used for writing very primitive parsers - really it is an internal detail of the library. The z type is the remaining unconsumed input.
runParser :: Parser a -> ByteString -> (Either String a, ByteString)Source
Apply a parser to an input token sequence.
Basic parsers
satisfy :: (Word8 -> Bool) -> Parser Word8Source
Return the next token if it satisfies the given predicate.
onFail :: Parser a -> Parser a -> Parser aSource
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.
onFail q
Derived parsers (but implemented more efficiently)
manySatisfy :: (Word8 -> Bool) -> Parser ByteStringSource
manySatisfy p is a more efficient fused version of many (satisfy p)
many1Satisfy :: (Word8 -> Bool) -> Parser ByteStringSource
many1Satisfy p is a more efficient fused version of many1 (satisfy p)
Re-parsing
reparse :: ByteString -> Parser ()Source
Push some tokens back onto the front of the input stream and reparse. This is useful e.g. for recursively expanding macros. When the user-parser recognises a macro use, it can lookup the macro expansion from the parse state, lex it, and then stuff the lexed expansion back down into the parser.