Re: [boost] Nasty compile time reflection and iteration for POD types using C++14 without macro

Subject: Re: [boost] Nasty compile time reflection and iteration for POD types using C++14 without macro
From: Klemens Morgenstern (klemens.morgenstern_at_[hidden])
Date: 2016-03-25 07:36:39

> I've tried to use __PRETTY_FUNCTION__ directly a year or two ago. Some
> compilers allowed that, some not.
>
> Could you try to compile that code on Clang? If that works, try to mark
> detail::ctti<T>::n() with constexpr and use in your code:

Clang 3.8 does compile with the example code.

>
>      template<std::size_t Index>
>      constexpr static char step()
>      {
>          return detail::ctti<T>::n()[Index];
>      }
>
> If that works, then it would be a really great addition to type_index!
>

That probably won't work. Constexpr [] on a const char* seems not to 
work, while "xyz"[1] works. That's why I use the __PRETTY_FUNC__ 
directly. Can be implemented that way though.

>
> That won't help. I need a way to make conversion of T type to some
> non-templated class and back:
> T -> int -> T
>
> TypeIndex allows only the first part of that: T -> type_index, but does not
> allow type_index -> T

Ah sure. Yeah then you can't get around some form of a macro. But maybe 
you could remove the index number, so adding a new class would work 
without that. That would allow me to add types at several places, 
because elsewise it might crash when different libraries do that. Though 
that would be a tweak later on.