Traits library

Trait as a normal function

Most of the standard traits are available in LTL. They are in the header ltl/traits.h

auto ptrInt = ltl::type_v<int*>;
auto typeChar = ltl::type_v<char>;
typed_static_assert(ltl::is_pointer(ptrInt));
typed_static_assert(ltl::is_pointer(typeChar));

True types are also available in this process:

int *p = nullptr;
typed_static_assert(ltl::is_pointer(p));

Concept like macro

Include the header ltl/concept.h. You can write:

template <typename T, requires_f(ltl::IsFloatingPoint<T>)> constexpr auto f(T) {
  return 0;
}

template <typename T, requires_f(ltl::IsIntegral<T>)> constexpr auto f(T) {
  return 1;
}

void test_concept() {
  static_assert(f(5) == 1);
  static_assert(f(5.0) == 0);
  static_assert(f(5.0f) == 0);
  static_assert(f(5u) == 1);
  static_assert(f(5ull) == 1);
}

For custom templated types, you can use LTL_MAKE_IS_KIND macro to generate appropriate traits and concept.

LTL_MAKE_IS_KIND(type, name, conceptName, kind of template);
LTL_MAKE_IS_KIND(std::optional, is_optional, IsOptional, typename);