Eric Niebler wrote:
Paul Mensonides wrote:
The only way to "have-your-cake-and eat-it-too" in the presence of macros like min/max is to prevent them from expanding manually with BOOST_PREVENT_MACRO_SUBSTITUTION.
int main() { using std::min; min BOOST_PREVENT_MACRO_SUBSTITUTION(1, 2); return 0; }
This yields ADL and local context (which includes std::min if necessary).
Thanks, Paul. That's correct. boost::std_min is defined as follows:
template< typename T > inline T const & std_min( T const & a, T const & b ) { using std::min; return min BOOST_PREVENT_MACRO_SUBSTITUTION ( a, b ); }
So a call to boost::std_min is essentially an unqualified call to min, with a using directive to pull in std::min. Since it's an unqualified call, ADL can also pull in additional overloads from different namespaces.
Maybe it's worth mentioning that it is only usefull for use in the namespace boost. IIUC there is no lookup in the local namespace and additional lookup in boost. I.e. it's not quite an unqualified call when used outside boost. Thomas