The incremental-parser library is yet another parser combinator library, providing the usual set of `Applicative`, `Alternative`, and `Monad` combinators. Apart from this, it has three twists that make it unique. #### Parsing incrementally First, the parser is incremental. Not only can it be fed its input in chunks, but in proper circumstances it can also provide its output in parsed 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. Apart from the usual combinators `many` and `some`, for example, there are `concatMany` and `concatSome` operators. ```haskell many :: Parser s r -> Parser s [r] concatMany :: (Monoid s, Monoid r) => Parser s r -> Parser s r ``` #### Arbitrary monoidal inputs The second weirdness, this one shared with [Picoparsec](http://hackage.haskell.org/package/picoparsec), 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, from the [monoid-subclasses](http://hackage.haskell.org/package/monoid-subclasses) package. In Parsec: ```haskell 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: ```haskell string :: ByteString -> Parser ByteString word8 :: Word8 -> Parser Word8 anyWord8 :: Parser Word8 ``` In incremental-parser and Picoparsec: ```haskell string :: (LeftCancellativeMonoid s, MonoidNull s) => s -> Parser s s token :: (Eq s, FactorialMonoid s) => s -> Parser s s anyToken :: FactorialMonoid s => Parser s s ``` #### Two `Alternative` alternatives 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`](http://hackage.haskell.org/package/base/docs/Text-ParserCombinators-ReadP.html#g:2) and [uu-parsinglib](http://hackage.haskell.org/package/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. The standard `<|>` operator from the `Alternative` class acts as one or the other of the above, depending on whether the first type parameter of `Parser` is `Symmetric` or `LeftBiasedLocal`.