James Ward | 22a4e15 | 2020-09-25 11:43:21 +0100 | [diff] [blame] | 1 | #ifndef MAPBOX_UTIL_VARIANT_VISITOR_HPP |
| 2 | #define MAPBOX_UTIL_VARIANT_VISITOR_HPP |
| 3 | |
| 4 | #include <utility> |
| 5 | |
| 6 | namespace mapbox { |
| 7 | namespace util { |
| 8 | |
| 9 | template <typename... Fns> |
| 10 | struct visitor; |
| 11 | |
| 12 | template <typename Fn> |
| 13 | struct visitor<Fn> : Fn |
| 14 | { |
| 15 | using Fn::operator(); |
| 16 | |
| 17 | template<typename T> |
| 18 | visitor(T&& fn) : Fn(std::forward<T>(fn)) {} |
| 19 | }; |
| 20 | |
| 21 | template <typename Fn, typename... Fns> |
| 22 | struct visitor<Fn, Fns...> : Fn, visitor<Fns...> |
| 23 | { |
| 24 | using Fn::operator(); |
| 25 | using visitor<Fns...>::operator(); |
| 26 | |
| 27 | template<typename T, typename... Ts> |
| 28 | visitor(T&& fn, Ts&&... fns) |
| 29 | : Fn(std::forward<T>(fn)) |
| 30 | , visitor<Fns...>(std::forward<Ts>(fns)...) {} |
| 31 | }; |
| 32 | |
| 33 | template <typename... Fns> |
| 34 | visitor<typename std::decay<Fns>::type...> make_visitor(Fns&&... fns) |
| 35 | { |
| 36 | return visitor<typename std::decay<Fns>::type...> |
| 37 | (std::forward<Fns>(fns)...); |
| 38 | } |
| 39 | |
| 40 | } // namespace util |
| 41 | } // namespace mapbox |
| 42 | |
| 43 | #endif // MAPBOX_UTIL_VARIANT_VISITOR_HPP |