cpp-lazy-stream/include/stream/detail/traits.h

//
//  traits.hpp
//  stream
//
//  Created by Sam Jaffe on 6/24/17.
//

#pragma once

#include <type_traits>
#include <utility>

#include <iterator/detail/traits.h>
#include <iterator/facade.h>

#include <stream/forward.h>

#include <stream/detail/macro.h>

namespace stream::detail {
template <typename C> using begin_t = decltype(std::begin(VAL(C)));
template <typename C> using end_t = decltype(std::end(VAL(C)));

template <typename C> using ref_t = decltype(*VAL(begin_t<C>));
template <typename C> using value_type = std::remove_reference_t<ref_t<C>>;
template <typename C> using cref_t = std::add_const_t<ref_t<C>>;

template <typename, typename = void> struct has_size : std::false_type {};
template <typename, typename = void> struct has_empty : std::false_type {};

template <typename C>
struct has_size<C, std::enable_if_t<std::is_integral_v<TYPE(C, size())>>>
    : std::true_type {};
template <typename C>
struct has_empty<C, std::enable_if_t<std::is_same_v<TYPE(C, empty()), bool>>>
    : std::true_type {};

template <typename It, typename S, typename = void>
struct is_comparable : std::false_type {};

template <typename It, typename S>
struct is_comparable<It, S, EXISTS(VAL(It) == VAL(S))> : std::true_type {};

template <typename It, typename S, typename = void>
struct is_sized_sentinel : std::false_type {};

template <typename It, typename S>
struct is_sized_sentinel<It, S, EXISTS(VAL(S) - VAL(It))> : std::true_type {};

template <typename C> constexpr bool has_size_v = has_size<C>{};
template <typename C> constexpr bool has_empty_v = has_empty<C>{};
template <typename It, typename S>
constexpr bool is_comparable_v = is_comparable<It, S>{};

template <typename S>
constexpr bool has_sentinal_v = !std::is_same_v<begin_t<S>, end_t<S>>;

template <typename S, template <typename...> class Iter, typename... Ts>
using sentinel_iterator =
    std::conditional_t<detail::has_sentinal_v<S>, detail::end_t<S>,
                       Iter<detail::begin_t<S>, Ts...>>;

template <typename It, typename S>
constexpr bool is_sized_sentinel_v = is_sized_sentinel<It, S>{};
}

#include <stream/detail/undef.h>