Re: [boost] [log] Boost.Log formal review closing down

Subject: Re: [boost] [log] Boost.Log formal review closing down
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2010-03-18 12:51:44

Andrey Semashev wrote:
> On 03/18/2010 12:32 AM, vicente.botet wrote:
> > Andrey Semashev wrote:
> >>    void my_formatter(std::ostream&  strm, logging::record
> >>       const&  rec)
> >>    {
> >>      logging::extract<  unsigned int>("LineID",
> >>        rec.attribute_values(),
> >>        lambda::var(strm)<<  lambda::_1<<  ": ");
> >>
> >>      logging::extract<  severity_level>(
> >>        "Severity",
> >>        rec.attribute_values(),
> >>        lambda::var(strm)<<  "<"<<  lambda::_1<<  ">  ");
> >>
> >>      strm<<  rec.message();
> >>    }
> >
> > Sorry I find this yet clearer
> >
> > void my_formatter(std::ostream&  strm, logging::record const&  rec)
> >    fmt::stream
> >      <<  attr<  unsigned int>("LineID")
> >      <<  ":<"<<  attr<  logging::severity_level>("Severity")
> >      <<  ">  "<<  message()
> > }
>
> Then the current lambda syntax is your friend.

Vicente's corrected version:

void
my_formatter(std::ostream & strm, logging::record const & rec)
{
  fmt::stream << rec.line_id() << ": <" << rec.severity_level()
    << "> " << rec.message()
}

I doubt the lambda version can be clearer than that and it would certainly lead to more chances to make hard to diagnose syntax mistakes.  Concerns from others about reinvention, in this case inventing your own lambda support, means that users cannot apply whatever knowledge they may have with using other lambda libraries to understanding errors in using yours.  Vicente's suggested syntax is clear, simple, and permits meaningful, direct compile diagnostics.  It is worth serious consideration.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

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