[boost] Boost.Exception helper

From: Tom Brinkman (reportbase_at_[hidden])
Date: 2007-10-03 10:53:26

>> typedef tags<tag_file_name,tag_open_mode,tag_errno> file_err;
>> throw my_error() << file_err(name,mode,errno);

Looks good.

I wonder why my_error() is required.  I wonder if a globaly
static object, such as "boost::exception()" might be even cleaner
and more lightweight. This would allow us to rewrite the throw statement like
the following:

try
{
      throw boost::exception() << file_err(name,mode,errno);
}
catch(boost::exception& e)
{
      std::cerr << e;
}