meta::default_constructible

Defined in header <mgs/meta/concepts/default_constructible.hpp>.

template <typename T>
concept default_constructible = meta::constructible_from<T>;

Pre-C++20 implementation of the std::default_constructible concept.

---

Concept emulation

namespace mgs {
namespace meta {

template <typename T>
struct is_default_constructible { /* ... */ };

template <typename T>
constexpr auto is_default_constructible_v = is_default_constructible<T>::value;

template <typename T,
          typename = std::enable_if_t<is_default_constructible_v<T>>>
using default_constructible = T;

} // namespace meta
} // namespace mgs

Example

#include <mgs/meta/concepts/default_constructible.hpp>

using namespace mgs::meta;

struct non_default_constructible {
  non_default_constructible() = delete;
};

static_assert(is_default_constructible_v<std::vector<int>>, "");
static_assert(is_default_constructible_v<int>, "");
static_assert(!is_default_constructible_v<non_default_constructible>, "");

See also

• meta::constructible_from