//! construct
rc_ptr( const rc_ptr& rhs )
: _ptr( rhs.get()){
add_ref();
}
rc_ptr( const rc_ptr<other_t>& rhs )
: _ptr(rhs.get()){
add_ref();
}
bool operator!=( const rc_ptr<T>& lhs , const rc_ptr<T>& rhs ) {
return lhs.get() != rhs.get();
}