meta::bidirectional_iterator¶

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

template <typename I>
concept bidirectional_iterator =
  meta::forward_iterator<I> &&
  meta::derived_from<meta::iter_concept<I>, std::bidirectional_iterator_tag> &&
  requires(I i) {
    { --i } -> meta::same_as<I&>;
    { i-- } -> meta::same_as<I>;
  };

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

Concept emulation¶

namespace mgs {
namespace meta {

template <typename I>
struct is_bidirectional_iterator { /* ... */ };

template <typename I>
constexpr auto is_bidirectional_iterator_v = is_bidirectional_iterator<I>::value;

template <typename I,
          typename = std::enable_if_t<is_bidirectional_iterator_v<I>>>
using bidirectional_iterator = I;

} // namespace meta
} // namespace mgs

Example¶

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

using namespace mgs::meta;

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

See also¶