blamario / input-parsers

input-parsers

An extension of the parsers library

The parsers library provides a number of subclasses of the Alternative type class, as well as lots of combinators useful for writing actual parsers.

What those classes like Parsing and CharParsing lack is the ability to express certain efficient parser primitives like Attoparsec's takeWhile. To rectify for this failing and enable more efficient parsers to be expressed, the present package input-parsers adds type classes InputParsing and InputCharParsing. The common characteristic of almost all their methods is that their parse result has the same type as the parser input, and is a prefix of the input.

The present package also exports the class DeterministicParsing, which provides a number of parser methods that are guaranteed to succeed with a single (typically longest possible) result. This is most useful for writing the lexical layer of a parser, but it can help avoid ambiguities and inefficiencies in general.

Finally, the package provides the class Position to abstract over the position the parser reached in the input stream.

input-parsers's Issues

Doesn't build with attoparsec 0.14.2

We probably need a more strict bound here?

[4 of 5] Compiling Text.Parser.Input ( src/Text/Parser/Input.hs, dist/build/Text/Parser/Input.dyn_o )

src/Text/Parser/Input.hs:400:10: error:
    • No instance for (LookAheadParsing Attoparsec.Char8.Parser)
        arising from the superclasses of an instance declaration
    • In the instance declaration for
        ‘InputParsing Attoparsec.Char8.Parser’
    |
400 | instance InputParsing Attoparsec.Parser where
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/Text/Parser/Input.hs:402:15: error:
                         (Data.Attoparsec.Internal.Types.Parser ByteString))
        arising from a use of ‘lookAhead’
    • In the expression: lookAhead Attoparsec.Char8.takeByteString
      In an equation for ‘getInput’:
          getInput = lookAhead Attoparsec.Char8.takeByteString
      In the instance declaration for
        ‘InputParsing Attoparsec.Char8.Parser’
    |
402 |    getInput = lookAhead Attoparsec.takeByteString
    |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/Text/Parser/Input.hs:412:10: error:
    • No instance for (CharParsing Attoparsec.Char8.Parser)
        arising from the superclasses of an instance declaration
    • In the instance declaration for
        ‘InputCharParsing Attoparsec.Char8.Parser’
    |
412 | instance InputCharParsing Attoparsec.Parser where
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

...

Build fails with binary dependency but without attoparsec

In src/Text/Parser/Input.hs:
The imports of Lazy and ByteString are guarded by an #ifdef MIN_VERSION_attoparsec. Later on (from line 460 on), a part of the code guarded by #ifdef MIN_VERSION_binary also makes use of these imports.

Example errors:

src/Text/Parser/Input.hs:462:41: error:
    Not in scope: type constructor or class ‘Lazy.ByteString’
    Neither ‘Control.Monad.Trans.RWS.Lazy’,
            ‘Control.Monad.Trans.State.Lazy’ nor ‘Control.Monad.Trans.Writer.Lazy’ exports ‘ByteString’.
    |
462 |    type ParserInput (Lazy Binary.Get) = Lazy.ByteString
    |                                         ^^^^^^^^^^^^^^^

src/Text/Parser/Input.hs:470:43: error:
    Not in scope: type constructor or class ‘ByteString’
    |
470 |    type ParserInput (Strict Binary.Get) = ByteString
    |                                           ^^^^^^^^^^