meta::sized_sentinel_for

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

template <typename S, typename I>
concept sized_sentinel_for =
  meta::sentinel_for<S, I> &&
  requires(I const& i, S const& s) {
    { s - i } -> meta::same_as<meta::iter_difference_t<I>>;
    { i - s } -> meta::same_as<meta::iter_difference_t<I>>;
  }
};

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

Differences with the C++20 version

  • There is no disable_sized_sentinel customization point.

Concept emulation

namespace mgs {
namespace meta {

template <typename S, typename I>
struct is_sized_sentinel { /* ... */ };

template <typename S, typename I>
constexpr auto is_sized_sentinel_v = is_sized_sentinel<S, I>::value;

template <typename S, typename I,
          typename = std::enable_if_t<is_sized_sentinel_v<S, I>>>
using sized_sentinel_for = S;

} // namespace meta
} // namespace mgs

Example

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

using namespace mgs::meta;

static_assert(is_sized_sentinel_for_v<char*, char*>, "");
static_assert(is_sized_sentinel_for_v<std::vector<int>::iterator, std::vector<int>::iterator>, "");
static_assert(!is_sized_sentinel_for_v<std::list<int>::iterator, std::list<int>::iterator>, "");