Re: Reminder: Review for Zach's parsing library starts on Feb 19th

From: Andrzej Krzemienski (akrzemi1_at_[hidden])
Date: 2024-02-26 17:07:06

pon., 26 lut 2024 o 17:05 Christian Mazakas via Boost <boost_at_[hidden]>
napisał(a):

> > I would recommend putting something like the above in the docs, where the
> > motivation for using rule parsers is listed. Currently it states "fix the
> > attribute type produced by a parser to something other than the default"
> > but what you sayin above is more: "prevent the parsers from doing things
> > that they would otherwise do".
>
> Ha, came online to say exactly this. I think that description of the
> problem being
> solved is more than satisfactory and illuminates the issue quite well.
>
> > I note that parsing a homogenous sequence to a std::set does work, at
> least
> > without rules:
> > https://godbolt.org/z/x57j1dq5T
> >
> > I was surprised to find that, in the context of other precautions,
> feeding
> > parsed data to a collection is performed via `insert` rather than
> > `push_back`.
> This is probably a holdover from the X3 days as this is who Spirit treats
> collections
> generically and, ironically, is done for the exact reason that `std::set`
> supports
> `insert(pos, val)`.
>
> In principle, I don't think that a free-form grammar like the above parsing
> into a `set`
> is problematic. Instead, I agree more with Zach that when you're formally
> defining rules,
> you're really telling the library, "Hey, this is exactly what I want to be
> parsing into."
>

I would be fine with this approach, except that I found the behavior in
Boost.Parser is more complicated than that.
I had a parser in Boost.Spirit V2 that does not use a single rule:
https://github.com/akrzemi1/wdungeon/blob/master/parser.cpp#L47

This does no longer work in Boost.Parser, because it imposes stricter rules
on attribute conversions *even when I do not use rules*.
So, I cannot build a simple conceptual model here.

Regards,
&rzej;

>
> - Christian
>
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