[boost] Phoenix V3 and Logging library help.

4 Jul 2011

      Hi Thomas, all,

I am researching about logging libraries.
I had to discard Boost.Log ( from Andrey) because this library does not
support GCC 3.4.
I've seen other libraries, but none convinced me.

I'm thinking of writing a simple logging library, and to avoid the use of
macros, I decided to do something like this:

namespace prototype1
{

namespace levels
{

boost::phoenix::expression::argument<1>::type const trace = {{{}}};
boost::phoenix::expression::argument<1>::type const debug = {{{}}};
boost::phoenix::expression::argument<1>::type const info = {{{}}};
boost::phoenix::expression::argument<1>::type const warn = {{{}}};
boost::phoenix::expression::argument<1>::type const error = {{{}}};
boost::phoenix::expression::argument<1>::type const fatal = {{{}}};

} //namespace levels

struct dynamic_logger
{
    template <typename Pred>
    void log( Pred const & pred ) const
    {
        streams_type::const_iterator it = streams_.begin();
        streams_type::const_iterator end = streams_.end();

        for ( ; it != end; ++it )
        {
            pred( **it );
        }
    }

    void add_target ( std::ostream & ostr )
    {
        streams_.push_back( &ostr );
    }

    typedef std::vector< std::ostream* > streams_type; //to improve
    streams_type streams_;
};

template <typename Logger, typename Pred>
void log( Logger & logger, Pred const & pred )
{
    return logger.log(pred);
}

} //namespace prototype1

int main(/*int argc, char* argv[]*/)
{
    {
        using namespace prototype1;
        using namespace prototype1::levels;

        std::ofstream outfile ("test.log");

        dynamic_logger dl;
        dl.add_target( std::cout );
        dl.add_target( outfile );

        dl.log ( info << "hello" << " world!" << std::endl );
        dl.log ( warn << "hello" << " world!" << std::endl );
        dl.log ( error << "hello" << " world!" << std::endl );

        log( dl, info "hello" << " world!" << std::endl ); //free function
    }

    return 0;
}

This code is a simple prototype,

This code is a prototype should be improved.
The questions are:

1. Does  PhoenixV3 (and Proto) supports GCC 3?
2. How to make the above code write the following ... ?

        INFO  - hello world!
        WARN  - hello world!
        ERROR - hello world!
        INFO  - hello world!

Is it possible?

The key is to identify the different Levels. (see namespace
prototype1::levels)

Please, suggestions and criticisms are welcome.

Note: I do not intend to compete with Boost.Log.

Thanks and regards,
Fernando Pelliccioni.