CTView.hpp

#pragma once
#include <concepts>

namespace CTC {
template <typename T>
concept Iterator = requires(std::remove_cvref_t<T> a, std::remove_cvref_t<T> b) {
    { a++ } -> std::same_as<std::remove_cvref_t<T>>;
    { *a };
    { a = b };
    { a == b } -> std::convertible_to<bool>;
};
template <typename T>
concept Iterable = requires(T a) {
    { a.begin() } -> std::convertible_to<decltype(a.end())>;
    { a.begin() } -> Iterator;
};

template <Iterator T>
struct View {
    T                         begin_;
    T                         end_;
    [[nodiscard]] auto&       begin() { return begin_; }
    [[nodiscard]] const auto& begin() const { return begin_; }
    [[nodiscard]] auto&       end() { return end_; }
    [[nodiscard]] const auto& end() const { return end_; }
};
template <Iterable T>
constexpr auto view_form_iterable(T& a) {
    return View{a.begin(), a.end()};
}

} // namespace CTC