On 21.04.2011 23:13, Stewart, Robert wrote:
Remember that "has_" implies ownership or inherent characteristic which doesn't apply to a namespace scope operator.
Class must have only intrinsic member functions, without which it doesn't working. Extended part of interface defines out of class body (perhaps in a separate module) in the same namespace, in terms of intrinsic member functions. This decrease coupling of code. (This C++ Software Construction approach was clearly described and proposed in Czarnecki/Eisenecker "Generative Programming". - S.Meyers agree; H.Sutter agree; D.Abrahams :) agree.) Consider Barton/Nackman trick as it presents in Boost.Operators library: boost::equality_comparable<T> require from T operator < is being defined (as member or free operator function, doesn't matter). Operators >, <=,
= are generated automatically as free operator functions due to inheritance.
But there is no difference between 4 operators <, >, <= and >= from point of view its meaning and "status": they all makes interface of class T. Operators >, <=, >= aren't second class citizens, even if operator < is define as member operator function. -- - Do you speak English? Мужик с глубоким вздохом: - Yes I do. А хули толку?