Re: [boost] "Simple C++11 metaprogramming"

Bruno Dutra wrote:

What you mean? std::decay<>::type is the lazy backend.

Eh, no, it's just an implementation detail. Change your template<> struct test_c<void>{using type = void;}; to template<> struct test_c<int>{using type = int;}; and then look at the following decay<> of mine, which I'm sure you'll agree really has no "lazy backend". template<class T> T make(); template<class T> T decay_impl(T); template<class T> using decay = decltype(decay_impl(make())); template<class T> using test2 = test; static_assert(is_evaluable::value, ""); static_assert(!is_evaluable::value, ""); static_assert(!is_evaluable::value, ""); is_evaluable still works as expected. It even works on decay<> directly: static_assert(is_evaluable::value, ""); static_assert(is_evaluable::value, ""); static_assert(!is_evaluable::value, ""); static_assert(!is_evaluable::value, "");