cpp-useful-iterators/include/iterator/detail/traits.h

#pragma once

#include <algorithm>
#include <iterator>
#include <type_traits>

#include <iterator/forwards.h>

#include <iterator/detail/macro.h>

// Section: Non-Dependant Typedef Helpers
namespace iterator::detail {
template <typename Iter>
using category_t = typename std::iterator_traits<Iter>::iterator_category;
template <typename C> using iter = decltype(std::begin(std::declval<C>()));
}

namespace iterator::detail {
// Type Helper for identifying container-like objects
template <typename C, typename = void> struct is_container : std::false_type {};
template <typename C>
struct is_container<C, std::void_t<iter<C>>> : std::true_type {};

template <typename It, typename = void>
struct sentinel_type {
  using type = void;
};
template <typename It>
struct sentinel_type<It, std::void_t<typename It::sentinel_type>> {
  using type = typename It::sentinel_type;
};
}

namespace iterator::detail {
template <typename C> constexpr bool is_container_v = is_container<C>{};

template <typename Iter>
constexpr bool is_rvalue_iterator_v = !std::is_reference_v<DEREF_TYPE(Iter)>;

template <typename It>
constexpr bool has_sentinel_type_v = !std::is_void_v<typename sentinel_type<It>::type>;

template <typename It, typename S>
constexpr bool is_sentinel_v = std::is_same_v<typename sentinel_type<It>::type, S>;
}

#include <iterator/detail/undef.h>