meta::forward_iterator¶

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

template <typename I>
concept forward_iterator =
   meta::input_iterator<I> &&
   meta::derived_from<meta::iter_concept<I>, std::forward_iterator_tag> &&
   meta::incrementable<I> &&
   meta::sentinel_for<I, I>;

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

Concept emulation¶

namespace mgs {
namespace meta {

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

template <typename I>
constexpr auto is_forward_iterator_v = is_forward_iterator<I>::value;

template <typename I,
          typename = std::enable_if_t<is_forward_iterator_v<I>>>
using forward_iterator = I;

} // namespace meta
} // namespace mgs

Example¶

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

using namespace mgs::meta;

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

See also¶