meta::readable¶

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

template <typename In>
concept readable =
  requires {
     typename meta::iter_value_t<In>;
     typename meta::iter_reference_t<In>;
     typename meta::iter_rvalue_reference_t<In>;
  } &&
  meta::common_reference_with<meta::iter_reference_t<In>&&, meta::iter_value_t<In>&> &&
  meta::common_reference_with<meta::iter_reference_t<In>&&, meta::iter_rvalue_reference_t<In>&&> &&
  meta::common_reference_with<meta::iter_rvalue_reference_t<In>&&, meta::iter_value_t<In> const&>;

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

Concept emulation¶

namespace mgs {
namespace meta {

template <typename In>
struct is_readable { /* ... */ };

template <typename In>
constexpr auto is_readable_v = is_readable<In>::value;

template <typename In,
          typename = std::enable_if_t<is_readable_v<In>>>
using readable = In;

} // namespace meta
} // namespace mgs

Example¶

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

using namespace mgs::meta;

static_assert(is_readable_v<std::string::iterator>, "");
static_assert(is_readable_v<char const*>, "");
static_assert(!is_readable_v<void*>, "");

See also¶