From: Stewart, Robert Let me clarify something that has just occurred to me. I've been writing strictly in the abstract about a compile time bounded type and a runtime bounded type and about names for them. I've not been making any specific references to your types as they now exist.
OK, sounds reasonable. The thing is that the "bounded" class template is universal and equally suitable for dynamic and static bounds. The only reason for existence of "bounded_int" is to save some typing when defining bounded types that have bounds expressible as compile time constant expressions. So instead of: bounded< int, boost::mpl::integral_c<int, 0>, boost::mpl::integral_c<int, 10> > you can just say: bounded_int<int, 0, 10> So yes - the "rt_bounded"/"ct_bounded" abstraction doesn't map to "bounded"/"bounded_int" and what I'm asking for is NOT a name for bounded class with bounds that don't change, but a better name for "bounded_int".
There are even cases when "bounded_int" cannot be used to define static bounds and you have to use "bounded" instead these are all the cases where the bounds cannot be expressed directly using compile time constant expressions, e.g. for floats or rational numbers. See the example with rational numbers in the second part of this subsection: <http://tinyurl.com/332vmf5#constrained_value.tutorial.compile_time_fixed_bounds>
In which case the type cannot be compile time bound and a runtime bound type must be used. I see no problem here.
Strictly speaking it's not a runtime bound. You cannot change the value of quarter2type object. It has no storage and only expresses some fixed value by its type, just like boost::mpl::integral_c does. Here's the difference (using types from the example above): bounded<rational>::type rt_rational; change_upper_bound(rt_rational, rational(1, 3)); // OK - can change bounds at runtime bounded<rational, quarter2type, half2type>::type ct_rational; change_upper_bound(ct_rational, rational(1, 3)); // COMPILATION ERROR!
Making things specific, I'd like to see your bounded class template be an implementation detail with two public types that use it to do the heavy lifting. (If you think that is insufficient for some reason, then expose all three with your current bounded class template being documented as the advanced form.)
I see no big advantage in doing so - the hypothetical "rt_bounded" class would then serve similar purpose as "bounded_int", that is wrapping "bounded" to save a few keystrokes, but as opposed to "bounded_int" it would save them only in rare cases (for instance when you would be overriding the default error policy) - most of the time there would be no difference, because defining a type with runtime bounds is as simple as: bounded<int>::type my_runtime_bounded_int; And for cases like rationals or floats with fixed bounds you would have to use "bounded" anyway, so it cannot become an implementation detail only.
From: vicente.botet Sorr bau I dont see the difference. I consider ratio<N,D> to express a compile time constant through a type, as integral_c or integral_constant do.
Sorry, maybe I've been unclear - by "compile time constant" I mean what C++ Standard describes as constant expression. Therefore, a type is not a compile time constant in this sense. Best regards, Robert