[boost] none.hpp

From: Joe Gottman (jgottman_at_[hidden])
Date: 2006-07-24 21:30:47

In order to avoid having an unnamed namespace inside a header file, none.hpp 
has been rewritten as

    namespace boost {
        none_t const none = ((none_t)0) ;
    } // namespace

But if two source files contain none.hpp won't this violate the 
one-definition rule?  What's wrong with defining none_t and none as follows:

namespace boost {
    enum none_t {none = 0};
}

This allows us to have a unique value boost::none of type boost::none_t that 
can be included in any number of source files without violating the ODR.

Joe Gottman