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Subject: Re: [std-proposals] Beyond regex
From: Dejan Milosavljevic (dmilos_at_[hidden])
Date: 2019-10-29 03:51:46


1. ... doesn't have any motivation.
- https://en.wikipedia.org/wiki/Lex_(software)
- https://en.wikipedia.org/wiki/Comparison_of_parser_generators
 Why so many libraries? C, C#, C++, Java, Haskell, Eiffel, Go.

2. Is the implementation useful to you/to-others?
 Implementation it self is useful for anyone. I documentation give
simple example. Is this example useful to you?
 Or to simplify completely in next example. In stream of characters
what is next to come: word or key-word? How to solve within existing
c++?
 Parse 1024 characters and then apply std::regex for word and
key-word(s)? Very inefficient (slow execution) not practical to code
and maintain.
 Let me generalize question: is `lex` useful? See: 1.

3. Have you tried implementing it?
 Yes and no.
 Yes. I implement my own `regex` and `lex` on the top of the that. No
one will use that because it is not rely on standard.
 No. Implementing `lex` in the top of std::rex require internal
knowledge for specific compiler vendor and compiler version.
   Standard does not require how implementation will look like. New
versions will arrives very fast. Any attempt to start is pointless
before start.

4. Open question: is there `regex_search` complexity guarantee?
 No one ask about this.

On Mon, Oct 28, 2019 at 3:40 PM Arthur O'Dwyer
<arthur.j.odwyer_at_[hidden]> wrote:
>
> On Sat, Oct 26, 2019 at 3:17 PM Dejan Milosavljevic via Std-Proposals <std-proposals_at_[hidden]> wrote:
>>
>> Hi,
>>
>> 1. Point of proposal is Lex it self. This is one of possible implementation.
>> 2. Open question: is there regex_search complexity guarantee?
>> 3. Next step should be something like `yacc`. Covering Type-2 or
>> Type-3 grammars will be very helpful.
>>
>> And as usual allow small inconsistency and incompleteness.
>>
>> Document: https://github.com/dmilos/cpp_proposal/blob/master/lex.md
>
>
> Received. I assume nobody's responding because it's not a very widely interesting proposal, and doesn't have any motivation.
> It sounds like you're describing a library that you could implement yourself and put on GitHub, where anyone could use it regardless of standardization. Have you tried implementing it? Is the implementation useful to you? Is the implementation useful to others?
>
> HTH,
> Arthur


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