[boost] Re: please read! min/max guidelines

From: Eric Niebler (eric_at_[hidden])
Date: 2004-02-29 02:24:28

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.

boost::std_min is nothing more than a convenience to keep you from 
littering your code with using statements and Ugly Macros. I might 
hazard to make a generalization here and suggest you prefer std_min to 
std::min because (a) chances are good you want ADL anyway, (b) std_min 
doesn't suffer from macro mish-mash, and (c) std_min is 1 fewer 
character to type when you're already in the boost namespace. :-)

Hope that makes sense now.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com