[boost] Boost.Exception helper

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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; }