optional.hpp 1.53 KB
Newer Older
1 2 3 4 5 6 7 8
#ifndef MAPBOX_UTIL_OPTIONAL_HPP
#define MAPBOX_UTIL_OPTIONAL_HPP

#pragma message("This implementation of optional is deprecated. See https://github.com/mapbox/variant/issues/64.")

#include <type_traits>
#include <utility>

9
#include "variant.hpp"
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

namespace mapbox {
namespace util {

template <typename T>
class optional
{
    static_assert(!std::is_reference<T>::value, "optional doesn't support references");

    struct none_type
    {
    };

    variant<none_type, T> variant_;

25
  public:
26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74
    optional() = default;

    optional(optional const& rhs)
    {
        if (this != &rhs)
        { // protect against invalid self-assignment
            variant_ = rhs.variant_;
        }
    }

    optional(T const& v) { variant_ = v; }

    explicit operator bool() const noexcept { return variant_.template is<T>(); }

    T const& get() const { return variant_.template get<T>(); }
    T& get() { return variant_.template get<T>(); }

    T const& operator*() const { return this->get(); }
    T operator*() { return this->get(); }

    optional& operator=(T const& v)
    {
        variant_ = v;
        return *this;
    }

    optional& operator=(optional const& rhs)
    {
        if (this != &rhs)
        {
            variant_ = rhs.variant_;
        }
        return *this;
    }

    template <typename... Args>
    void emplace(Args&&... args)
    {
        variant_ = T{std::forward<Args>(args)...};
    }

    void reset() { variant_ = none_type{}; }

}; // class optional

} // namespace util
} // namespace mapbox

#endif // MAPBOX_UTIL_OPTIONAL_HPP