meta::forward_range¶

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

template <typename T>
concept forward_range =
  meta::input_range<T> && meta::forward_iterator<meta::iterator_t<T>>;

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

Concept emulation¶

namespace mgs {
namespace meta {

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

template <typename T>
constexpr auto is_forward_range_v = is_forward_range<T>::value;

template <typename T,
          typename = std::enable_if_t<is_forward_range_v<T>>>
using forward_range = T;

} // namespace meta
} // namespace mgs

Example¶

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

using namespace mgs::meta;

struct dummy_input_range {
  std::istreambuf_iterator<char> begin();
  std::istreambuf_iterator<char> end();
};

static_assert(is_forward_range_v<std::forward_list<char>>, "");
static_assert(is_forward_range_v<char [2]>, "");
static_assert(!is_forward_range_v<dummy_input_range>, "");

See also¶