From: Vladimir Prus <ghost@cs.msu.su>
While it's generally considered a bad practice to provide implicit conversions, I think it would be good to provide such a conversion for the boost::format class. Currently, I can't write:
string s; s = format("%1%") % 10;
and need to write
s = (format("%1%") % 10).str();
Maybe it's specifics of my code, but I can count 10 such conversions in a single source file. I think that:
1. Calling .str() is rather inconvenient. 2. The 'format' class most often used inside expressions. It's not likely to be passed around to functions and so the dangers of implicit conversions are not critical.
While your usage might be proven normative and thus could be used to justify adding an implicit conversion, how about another approach? Why not add a non-member function str() or to_string(): template <class T> std::string boost::str(T const & source_i) { return source_i.str(); } Then, you example becomes: s = str(format("%1%") % 10); (I don't even know the types involved in your expression to make a non-templated function. Besides, I thought this might be generally useful.) To generalize further (warning: uncompiled, untested code): template <class T> typename boost::result_of<&T::str()>::type boost::str(T const & source_i) { return source_i.str(); } That would be more flexible. This could also be the primary template specialization and it could be specialized for other types that don't provide a str() member function. -- Rob Stewart stewart@sig.com Software Engineer http://www.sig.com Susquehanna International Group, LLP using std::disclaimer;