add static which<T>() function to get a contained types' which value

mapbox · Jun 1, 2016 · 74ce146 · 74ce146
1 parent 2f8a4a3
commit 74ce146
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/include/mapbox/variant.hpp b/include/mapbox/variant.hpp
@@ -780,6 +780,13 @@ class variant
         return static_cast<int>(sizeof...(Types)-type_index - 1);
     }
 
+    template <typename T, typename std::enable_if<
+                              (detail::direct_type<T, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE static constexpr int which() noexcept
+    {
+        return static_cast<int>(sizeof...(Types)-detail::direct_type<T, Types...>::index - 1);
+    }
+
     // visitor
     // unary
     template <typename F, typename V, typename R = typename detail::result_of_unary_visit<F, first_type>::type>