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Subject: Re: [boost] [log][phoenix] Questions on porting to phoenix
From: TONGARI (tongari95_at_[hidden])
Date: 2012-01-23 05:37:56

Hi Andrey,

2012/1/23 Andrey Semashev <andrey.semashev_at_[hidden]>

> Hi,
> [My apologies for the long post]
> I'm trying to port filters and formatters of Boost.Log to Boost.Phoenix

That's exciting :-)


What I'm trying to achieve is something along these lines (this is not a
> finalized interface yet):
> enum my_severity { info, warning, error };
> BOOST_LOG_REGISTER_ATTRIBUTE("Severity", severity, my_severity)
> filter flt = severity >= warning;
> formatter fmt = stream << "[" << severity << "] " << message;
> Here, "stream" and "message" are keywords provided by Boost.Log, the
> former is
> a placeholder for the stream argument of the formatter function, and the
> latter returns the result of the record::message() method.
> Now, the BOOST_LOG_REGISTER_ATTRIBUTE macro is what I'm struggling on. It
> should create a new keyword (severity) which should:
> 1. Be a POD object to be statically initialized.
> 2. Contain the information on the type (my_severity) and name ("Severity")
> of
> the attribute to be able to extract it from the log record.
> 3. Be a Phoenix object to initiate lazy expression generation.

I wrote the sample code that conforms these requirements, full code

> >From what I gathered from the docs and examples, the generated keyword
> should
> be a terminal, in terms of Proto. Am I correct?

I think it's a phoenix actor which is also a proto terminal.

In order to produce the value,
> during the evaluation the keyword should receive either a log record or a
> attribute_values_view and I can't quite understand how do I do that.
> Basically, I don't quite understand how do I declare and implement a
> terminal
> so that it works with Phoenix. This question also applies to the "stream"
> and
> "message" keywords but I suspect the solution will be similar.
> Maybe there is an example of doing this in the docs or elsewhere. I'll be
> glad
> if someone provides a link or example of doing this. Thanks in advance.


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