ANNOUNCE: incremental-parser library package

[S. Doaitse Swierstra]

Can you explain what are the advantages of your library over the online version of all applicative parsers in the uu-parsinglib, which are not restricted to the monoidal results?


On 22 mrt 2011, at 15:14, Mario Blažević wrote:

>     The first version of incremental-parser has been released on Hackage [1]. It's yet another parser combinator
> library, providing the usual set of Applicative and Monad combinators. Apart from this, it has three twists that make it
> unique.
> 
>     First, the parser is incremental. That means it can be fed its input in chunks, and in proper circumstances it can
> also provide the parsed output in chunks. For this to be possible the result type must be a Monoid. The complete parsing
> result is then a concatenation of the partial results.
> 
>     In order to make the incremental parsing easier, the combinator set is optimized for monoidal results. The usual
> combinator many1, for example, assumes the result type is a monoid and concatenates its components instead of
> constructing a list.
> 
> In Parsec:
> > many1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m [a]
> 
> In incremental-parser:
> > many1 :: (Monoid s, Monoid r) => Parser s r -> Parser s r
> 
> 
>     The second weirdness is that the the parser is generic in its input stream type, but this type is parameterized in a
> holistic way. There is no separate token type. Primitive parsers that need to peek into the input require its type to be
> an instance of a monoid subclass.
> 
> In Parsec:
> > string :: Stream s m Char => String -> ParsecT s u m String
> > char :: Stream s m Char => Char -> ParsecT s u m Char
> > anyToken :: (Stream s m t, Show t) => ParsecT s u m t
> 
> In Attoparsec:
> > string :: ByteString -> Parser ByteString
> > word8 :: Word8 -> Parser Word8
> > anyWord8 :: Parser Word8
> 
> In incremental-parser:
> > string :: (LeftCancellativeMonoid s, MonoidNull s) => s -> Parser s s
> > token :: (Eq s, FactorialMonoid s) => s -> Parser s s
> > anyToken :: FactorialMonoid s => Parser s s
> 
>     The monoid subclasses referenced above provide methods for analyzing and subdividing the input stream. The classes
> are not particularly demanding, and any reasonable input stream should be able to accommodate them easily. The library
> comes with instances for lists, ByteString, and Text.
> 
> > class Monoid m => MonoidNull m where
> >    mnull :: m -> Bool
> 
> > class Monoid m => LeftCancellativeMonoid m where
> >    mstripPrefix :: m -> m -> Maybe m
> 
> > class Monoid m => FactorialMonoid m where
> >    factors :: m -> [m]
> >    primePrefix :: m -> m
> >    ...
> 
> 
>     Finally, the library being implemented on the basis of Brzozowski derivatives, it can provide both the symmetric and
> the left-biased choice, <|> and <<|>. This is the same design choice made by Text.ParserCombinators.ReadP and
> uu-parsinglib. Parsec and its progeny on the other hand provide only the faster left-biased choice, at some cost to the
> expressiveness of the combinator language.
> 
> [1] http://hackage.haskell.org/package/incremental-parser-0.1
> 
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