Hi,
Use
void initialize(value_type & value_o);
rather than
value_type initialize();
Thus, when passed the data member to initialize, it can initialize that object directly. Granted, (N)RVO can often avoid the copy, but this change will ensure you get the efficiency.
I don't think so, because your version of initialize couldn't be used to initialize a value in constructor's initialization list. So first the value would be default-constructed, and then assigned another value using initialize. In bounded policies I use passed_value_type initialize() where passed_value_type is value_type for integral types and const value_type & for other types. The second returns a reference to a static object - that's the most efficient method I can think of, initialization takes only one copy-construction (for details please look into the code).
Putting it simply, point of my library is to provide templates of classes of objects having a value conforming to given constraints. constrained_type (or whatever we'll call it) is a type (class template to be strict), how can a type be named "something_value"? Now that's confusing to me... Maybe constrained_values_type would be the most appropriate ;-)
What you are suggesting is equivalent to suggesting that std::vector should be named "vector_type" because it is a class template.
The purpose of the class template is to create objects through instantiating specializations. It is those objects that are actually used. Thus, the type name should be indicative of the purpose and use of those objects. Those objects are values. The class name should indicate the value nature of those objects.
Uhh, maybe you're right ;-) I don't know why, but it just "byte my eyes" when I see a type named "something_value"... Nevermind, if people here really resist that it should be called constrained_value instead of constrained_type, then OK - I'll change it. Best regards, Robert