You may have noted that there can be a case where using the DistProxy class might lead to worse performance—if the user of the class were to use the Point class like this, that is, if the std::sqrt() method were invoked multiple times according to the programmer's requests for the distance value:
auto a = Point{23, 42};
auto b = Point{33, 12};
auto dist = a.distance(b);
float dist_float0 = dist; // Assignment invoked std::sqrt()
float dist_float1 = dist; // std::sqrt() of dist is invoked again
Although a stupid example, there can be real-world cases where this might happen, and we want to force the user to only invoke operator float() once per DistProxy object. In order to prevent this we make the operator ...
