Arno Schödl wrote:
I am happy with members.
I'm glad we've reached a consensus :-) Would you like to officially create a request ticket for those three member functions, at https://svn.boost.org/trac/boost/newticket ? Otherwise I wouldn't mind doing so.
Just for my understanding, why are optional_swap and optional_move_to not expressible as free functions?
template< class T, class U > bool optional_move( T& t, boost::optional<U>& u ) { if( u ) { t=*u; return true; } else { return false; } };
template< class T > bool optional_move( T& t, boost::optional<T>& u ) { if( u ) { swap( t, *u ); return true; } else { return false; } };
{ int i; boost::optional<int> j=1; optional_move( i, j ); // swaps } { double i; boost::optional<int> j=1; optional_move( i, j ); // assigns with implicit conversion }
What am I missing?
Your original use case, from your very first posting on this subject! boost::optional< TMyValue > TryToGetT(); T t; // Would not compile, trying to pass an optional<T> rvalue! if( !optional_move( t, TryToGetT () ) { // ... other way to get t ... } The following would compile though, even if optional<T>::optional_move_to(T&) is non-const: if( ! TryToGetT().optional_move_to(t) { // ... other way to get t ... } HTH, Niels