6 files changed, 1422 insertions, 0 deletions
diff --git a/src/mapbox/optional.hpp b/src/mapbox/optional.hpp
new file mode 100644
index 0000000..d84705c
--- /dev/null
+++ b/src/mapbox/optional.hpp
@@ -0,0 +1,74 @@
+#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>
+
+#include <mapbox/variant.hpp>
+
+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_;
+
+public:
+    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
diff --git a/src/mapbox/recursive_wrapper.hpp b/src/mapbox/recursive_wrapper.hpp
new file mode 100644
index 0000000..4ffcbd7
--- /dev/null
+++ b/src/mapbox/recursive_wrapper.hpp
@@ -0,0 +1,122 @@
+#ifndef MAPBOX_UTIL_RECURSIVE_WRAPPER_HPP
+#define MAPBOX_UTIL_RECURSIVE_WRAPPER_HPP
+
+// Based on variant/recursive_wrapper.hpp from boost.
+//
+// Original license:
+//
+// Copyright (c) 2002-2003
+// Eric Friedman, Itay Maman
+//
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#include <cassert>
+#include <utility>
+
+namespace mapbox {
+namespace util {
+
+template <typename T>
+class recursive_wrapper
+{
+
+    T* p_;
+
+    void assign(T const& rhs)
+    {
+        this->get() = rhs;
+    }
+
+public:
+    using type = T;
+
+    /**
+     * Default constructor default initializes the internally stored value.
+     * For POD types this means nothing is done and the storage is
+     * uninitialized.
+     *
+     * @throws std::bad_alloc if there is insufficient memory for an object
+     *         of type T.
+     * @throws any exception thrown by the default constructur of T.
+     */
+    recursive_wrapper()
+        : p_(new T){}
+
+    ~recursive_wrapper() noexcept { delete p_; }
+
+    recursive_wrapper(recursive_wrapper const& operand)
+        : p_(new T(operand.get())) {}
+
+    recursive_wrapper(T const& operand)
+        : p_(new T(operand)) {}
+
+    recursive_wrapper(recursive_wrapper&& operand)
+        : p_(new T(std::move(operand.get()))) {}
+
+    recursive_wrapper(T&& operand)
+        : p_(new T(std::move(operand))) {}
+
+    inline recursive_wrapper& operator=(recursive_wrapper const& rhs)
+    {
+        assign(rhs.get());
+        return *this;
+    }
+
+    inline recursive_wrapper& operator=(T const& rhs)
+    {
+        assign(rhs);
+        return *this;
+    }
+
+    inline void swap(recursive_wrapper& operand) noexcept
+    {
+        T* temp = operand.p_;
+        operand.p_ = p_;
+        p_ = temp;
+    }
+
+    recursive_wrapper& operator=(recursive_wrapper&& rhs) noexcept
+    {
+        swap(rhs);
+        return *this;
+    }
+
+    recursive_wrapper& operator=(T&& rhs)
+    {
+        get() = std::move(rhs);
+        return *this;
+    }
+
+    T& get()
+    {
+        assert(p_);
+        return *get_pointer();
+    }
+
+    T const& get() const
+    {
+        assert(p_);
+        return *get_pointer();
+    }
+
+    T* get_pointer() { return p_; }
+
+    const T* get_pointer() const { return p_; }
+
+    operator T const&() const { return this->get(); }
+
+    operator T&() { return this->get(); }
+
+}; // class recursive_wrapper
+
+template <typename T>
+inline void swap(recursive_wrapper<T>& lhs, recursive_wrapper<T>& rhs) noexcept
+{
+    lhs.swap(rhs);
+}
+} // namespace util
+} // namespace mapbox
+
+#endif // MAPBOX_UTIL_RECURSIVE_WRAPPER_HPP
diff --git a/src/mapbox/variant.hpp b/src/mapbox/variant.hpp
new file mode 100644
index 0000000..06a46ab
--- /dev/null
+++ b/src/mapbox/variant.hpp
@@ -0,0 +1,1053 @@
+#ifndef MAPBOX_UTIL_VARIANT_HPP
+#define MAPBOX_UTIL_VARIANT_HPP
+
+#include <cassert>
+#include <cstddef>   // size_t
+#include <new>       // operator new
+#include <stdexcept> // runtime_error
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <typeinfo>
+#include <utility>
+#include <functional>
+#include <limits>
+
+#include <mapbox/recursive_wrapper.hpp>
+#include <mapbox/variant_visitor.hpp>
+
+// clang-format off
+// [[deprecated]] is only available in C++14, use this for the time being
+#if __cplusplus <= 201103L
+# ifdef __GNUC__
+#  define MAPBOX_VARIANT_DEPRECATED __attribute__((deprecated))
+# elif defined(_MSC_VER)
+#  define MAPBOX_VARIANT_DEPRECATED __declspec(deprecated)
+# else
+#  define MAPBOX_VARIANT_DEPRECATED
+# endif
+#else
+#  define MAPBOX_VARIANT_DEPRECATED [[deprecated]]
+#endif
+
+
+#ifdef _MSC_VER
+// https://msdn.microsoft.com/en-us/library/bw1hbe6y.aspx
+# ifdef NDEBUG
+#  define VARIANT_INLINE __forceinline
+# else
+#  define VARIANT_INLINE //__declspec(noinline)
+# endif
+#else
+# ifdef NDEBUG
+#  define VARIANT_INLINE //inline __attribute__((always_inline))
+# else
+#  define VARIANT_INLINE __attribute__((noinline))
+# endif
+#endif
+// clang-format on
+
+// Exceptions
+#if defined( __EXCEPTIONS) || defined( _MSC_VER)
+#define HAS_EXCEPTIONS
+#endif
+
+#define VARIANT_MAJOR_VERSION 1
+#define VARIANT_MINOR_VERSION 1
+#define VARIANT_PATCH_VERSION 0
+
+#define VARIANT_VERSION (VARIANT_MAJOR_VERSION * 100000) + (VARIANT_MINOR_VERSION * 100) + (VARIANT_PATCH_VERSION)
+
+namespace mapbox {
+namespace util {
+
+// XXX This should derive from std::logic_error instead of std::runtime_error.
+//     See https://github.com/mapbox/variant/issues/48 for details.
+class bad_variant_access : public std::runtime_error
+{
+
+public:
+    explicit bad_variant_access(const std::string& what_arg)
+        : runtime_error(what_arg) {}
+
+    explicit bad_variant_access(const char* what_arg)
+        : runtime_error(what_arg) {}
+
+}; // class bad_variant_access
+
+#if !defined(MAPBOX_VARIANT_MINIMIZE_SIZE)
+using type_index_t = unsigned int;
+#else
+#if defined(MAPBOX_VARIANT_OPTIMIZE_FOR_SPEED)
+using type_index_t = std::uint_fast8_t;
+#else
+using type_index_t = std::uint_least8_t;
+#endif
+#endif
+
+namespace detail {
+
+static constexpr type_index_t invalid_value = type_index_t(-1);
+
+template <typename T, typename... Types>
+struct direct_type;
+
+template <typename T, typename First, typename... Types>
+struct direct_type<T, First, Types...>
+{
+    static constexpr type_index_t index = std::is_same<T, First>::value
+        ? sizeof...(Types)
+        : direct_type<T, Types...>::index;
+};
+
+template <typename T>
+struct direct_type<T>
+{
+    static constexpr type_index_t index = invalid_value;
+};
+
+#if __cpp_lib_logical_traits >= 201510L
+
+using std::conjunction;
+using std::disjunction;
+
+#else
+
+template <typename...>
+struct conjunction : std::true_type {};
+
+template <typename B1>
+struct conjunction<B1> : B1 {};
+
+template <typename B1, typename B2>
+struct conjunction<B1, B2> : std::conditional<B1::value, B2, B1>::type {};
+
+template <typename B1, typename... Bs>
+struct conjunction<B1, Bs...> : std::conditional<B1::value, conjunction<Bs...>, B1>::type {};
+
+template <typename...>
+struct disjunction : std::false_type {};
+
+template <typename B1>
+struct disjunction<B1> : B1 {};
+
+template <typename B1, typename B2>
+struct disjunction<B1, B2> : std::conditional<B1::value, B1, B2>::type {};
+
+template <typename B1, typename... Bs>
+struct disjunction<B1, Bs...> : std::conditional<B1::value, B1, disjunction<Bs...>>::type {};
+
+#endif
+
+template <typename T, typename... Types>
+struct convertible_type;
+
+template <typename T, typename First, typename... Types>
+struct convertible_type<T, First, Types...>
+{
+    static constexpr type_index_t index = std::is_convertible<T, First>::value
+        ? disjunction<std::is_convertible<T, Types>...>::value ? invalid_value : sizeof...(Types)
+        : convertible_type<T, Types...>::index;
+};
+
+template <typename T>
+struct convertible_type<T>
+{
+    static constexpr type_index_t index = invalid_value;
+};
+
+template <typename T, typename... Types>
+struct value_traits
+{
+    using value_type = typename std::remove_const<typename std::remove_reference<T>::type>::type;
+    using value_type_wrapper = recursive_wrapper<value_type>;
+    static constexpr type_index_t direct_index = direct_type<value_type, Types...>::index;
+    static constexpr bool is_direct = direct_index != invalid_value;
+    static constexpr type_index_t index_direct_or_wrapper = is_direct ? direct_index : direct_type<value_type_wrapper, Types...>::index;
+    static constexpr bool is_direct_or_wrapper = index_direct_or_wrapper != invalid_value;
+    static constexpr type_index_t index = is_direct_or_wrapper ? index_direct_or_wrapper : convertible_type<value_type, Types...>::index;
+    static constexpr bool is_valid = index != invalid_value;
+    static constexpr type_index_t tindex = is_valid ? sizeof...(Types)-index : 0;
+    using target_type = typename std::tuple_element<tindex, std::tuple<void, Types...>>::type;
+};
+
+template <typename Src, typename Dest>
+struct copy_cvref
+{
+    using type = Dest;
+};
+
+template <typename Src, typename Dest>
+struct copy_cvref<Src const&, Dest>
+{
+    using type = Dest const&;
+};
+
+template <typename Src, typename Dest>
+struct copy_cvref<Src&, Dest>
+{
+    using type = Dest&;
+};
+
+template <typename Src, typename Dest>
+struct copy_cvref<Src&&, Dest>
+{
+    using type = Dest&&;
+};
+
+template <typename F, typename = void>
+struct deduced_result_type
+{};
+
+template <typename F, typename... Args>
+struct deduced_result_type<F(Args...), decltype((void)std::declval<F>()(std::declval<Args>()...))>
+{
+    using type = decltype(std::declval<F>()(std::declval<Args>()...));
+};
+
+template <typename F, typename = void>
+struct visitor_result_type : deduced_result_type<F>
+{};
+
+// specialization for explicit result_type member in visitor class
+template <typename F, typename... Args>
+struct visitor_result_type<F(Args...), decltype((void)std::declval<typename std::decay<F>::type::result_type>())>
+{
+    using type = typename std::decay<F>::type::result_type;
+};
+
+template <typename F, typename T>
+using result_of_unary_visit = typename visitor_result_type<F&&(T&&)>::type;
+
+template <typename F, typename T>
+using result_of_binary_visit = typename visitor_result_type<F&&(T&&, T&&)>::type;
+
+template <type_index_t arg1, type_index_t... others>
+struct static_max;
+
+template <type_index_t arg>
+struct static_max<arg>
+{
+    static const type_index_t value = arg;
+};
+
+template <type_index_t arg1, type_index_t arg2, type_index_t... others>
+struct static_max<arg1, arg2, others...>
+{
+    static const type_index_t value = arg1 >= arg2 ? static_max<arg1, others...>::value : static_max<arg2, others...>::value;
+};
+
+template <typename... Types>
+struct variant_helper;
+
+template <typename T, typename... Types>
+struct variant_helper<T, Types...>
+{
+    VARIANT_INLINE static void destroy(const type_index_t type_index, void* data)
+    {
+        if (type_index == sizeof...(Types))
+        {
+            reinterpret_cast<T*>(data)->~T();
+        }
+        else
+        {
+            variant_helper<Types...>::destroy(type_index, data);
+        }
+    }
+
+    VARIANT_INLINE static void move(const type_index_t old_type_index, void* old_value, void* new_value)
+    {
+        if (old_type_index == sizeof...(Types))
+        {
+            new (new_value) T(std::move(*reinterpret_cast<T*>(old_value)));
+        }
+        else
+        {
+            variant_helper<Types...>::move(old_type_index, old_value, new_value);
+        }
+    }
+
+    VARIANT_INLINE static void copy(const type_index_t old_type_index, const void* old_value, void* new_value)
+    {
+        if (old_type_index == sizeof...(Types))
+        {
+            new (new_value) T(*reinterpret_cast<const T*>(old_value));
+        }
+        else
+        {
+            variant_helper<Types...>::copy(old_type_index, old_value, new_value);
+        }
+    }
+};
+
+template <>
+struct variant_helper<>
+{
+    VARIANT_INLINE static void destroy(const type_index_t, void*) {}
+    VARIANT_INLINE static void move(const type_index_t, void*, void*) {}
+    VARIANT_INLINE static void copy(const type_index_t, const void*, void*) {}
+};
+
+template <typename T>
+struct unwrapper
+{
+    using value_type = T;
+
+    template <typename V>
+    static auto apply(typename std::remove_reference<V>::type& var)
+        -> typename std::enable_if<std::is_lvalue_reference<V>::value,
+                    decltype(var.template get_unchecked<T>())>::type
+    {
+        return var.template get_unchecked<T>();
+    }
+
+    template <typename V>
+    static auto apply(typename std::remove_reference<V>::type& var)
+        -> typename std::enable_if<!std::is_lvalue_reference<V>::value,
+                    decltype(std::move(var.template get_unchecked<T>()))>::type
+    {
+        return std::move(var.template get_unchecked<T>());
+    }
+};
+
+template <typename T>
+struct unwrapper<recursive_wrapper<T>> : unwrapper<T>
+{};
+
+template <typename T>
+struct unwrapper<std::reference_wrapper<T>> : unwrapper<T>
+{};
+
+template <typename R, typename... Types>
+struct dispatcher;
+
+template <typename R, typename T, typename... Types>
+struct dispatcher<R, T, Types...>
+{
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& v, F&& f)
+    {
+        if (v.template is<T>())
+        {
+            return std::forward<F>(f)(unwrapper<T>::template apply<V>(v));
+        }
+        else
+        {
+            return dispatcher<R, Types...>::apply(std::forward<V>(v), std::forward<F>(f));
+        }
+    }
+};
+
+template <typename R, typename T>
+struct dispatcher<R, T>
+{
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& v, F&& f)
+    {
+        return std::forward<F>(f)(unwrapper<T>::template apply<V>(v));
+    }
+};
+
+template <typename R, typename T, typename... Types>
+struct binary_dispatcher_rhs;
+
+template <typename R, typename T0, typename T1, typename... Types>
+struct binary_dispatcher_rhs<R, T0, T1, Types...>
+{
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& lhs, V&& rhs, F&& f)
+    {
+        if (rhs.template is<T1>()) // call binary functor
+        {
+            return std::forward<F>(f)(unwrapper<T0>::template apply<V>(lhs),
+                                      unwrapper<T1>::template apply<V>(rhs));
+        }
+        else
+        {
+            return binary_dispatcher_rhs<R, T0, Types...>::apply(std::forward<V>(lhs),
+                                                                 std::forward<V>(rhs),
+                                                                 std::forward<F>(f));
+        }
+    }
+};
+
+template <typename R, typename T0, typename T1>
+struct binary_dispatcher_rhs<R, T0, T1>
+{
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& lhs, V&& rhs, F&& f)
+    {
+        return std::forward<F>(f)(unwrapper<T0>::template apply<V>(lhs),
+                                  unwrapper<T1>::template apply<V>(rhs));
+    }
+};
+
+template <typename R, typename T, typename... Types>
+struct binary_dispatcher_lhs;
+
+template <typename R, typename T0, typename T1, typename... Types>
+struct binary_dispatcher_lhs<R, T0, T1, Types...>
+{
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& lhs, V&& rhs, F&& f)
+    {
+        if (lhs.template is<T1>()) // call binary functor
+        {
+            return std::forward<F>(f)(unwrapper<T1>::template apply<V>(lhs),
+                                      unwrapper<T0>::template apply<V>(rhs));
+        }
+        else
+        {
+            return binary_dispatcher_lhs<R, T0, Types...>::apply(std::forward<V>(lhs),
+                                                                 std::forward<V>(rhs),
+                                                                 std::forward<F>(f));
+        }
+    }
+};
+
+template <typename R, typename T0, typename T1>
+struct binary_dispatcher_lhs<R, T0, T1>
+{
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& lhs, V&& rhs, F&& f)
+    {
+        return std::forward<F>(f)(unwrapper<T1>::template apply<V>(lhs),
+                                  unwrapper<T0>::template apply<V>(rhs));
+    }
+};
+
+template <typename R, typename... Types>
+struct binary_dispatcher;
+
+template <typename R, typename T, typename... Types>
+struct binary_dispatcher<R, T, Types...>
+{
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& v0, V&& v1, F&& f)
+    {
+        if (v0.template is<T>())
+        {
+            if (v1.template is<T>())
+            {
+                return std::forward<F>(f)(unwrapper<T>::template apply<V>(v0),
+                                          unwrapper<T>::template apply<V>(v1)); // call binary functor
+            }
+            else
+            {
+                return binary_dispatcher_rhs<R, T, Types...>::apply(std::forward<V>(v0),
+                                                                    std::forward<V>(v1),
+                                                                    std::forward<F>(f));
+            }
+        }
+        else if (v1.template is<T>())
+        {
+            return binary_dispatcher_lhs<R, T, Types...>::apply(std::forward<V>(v0),
+                                                                std::forward<V>(v1),
+                                                                std::forward<F>(f));
+        }
+        return binary_dispatcher<R, Types...>::apply(std::forward<V>(v0),
+                                                     std::forward<V>(v1),
+                                                     std::forward<F>(f));
+    }
+};
+
+template <typename R, typename T>
+struct binary_dispatcher<R, T>
+{
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& v0, V&& v1, F&& f)
+    {
+        return std::forward<F>(f)(unwrapper<T>::template apply<V>(v0),
+                                  unwrapper<T>::template apply<V>(v1)); // call binary functor
+    }
+};
+
+// comparator functors
+struct equal_comp
+{
+    template <typename T>
+    bool operator()(T const& lhs, T const& rhs) const
+    {
+        return lhs == rhs;
+    }
+};
+
+struct less_comp
+{
+    template <typename T>
+    bool operator()(T const& lhs, T const& rhs) const
+    {
+        return lhs < rhs;
+    }
+};
+
+template <typename Variant, typename Comp>
+class comparer
+{
+public:
+    explicit comparer(Variant const& lhs) noexcept
+        : lhs_(lhs) {}
+    comparer& operator=(comparer const&) = delete;
+    // visitor
+    template <typename T>
+    bool operator()(T const& rhs_content) const
+    {
+        T const& lhs_content = lhs_.template get_unchecked<T>();
+        return Comp()(lhs_content, rhs_content);
+    }
+
+private:
+    Variant const& lhs_;
+};
+
+// hashing visitor
+struct hasher
+{
+    template <typename T>
+    std::size_t operator()(const T& hashable) const
+    {
+        return std::hash<T>{}(hashable);
+    }
+};
+
+} // namespace detail
+
+struct no_init {};
+
+template <typename... Types>
+class variant
+{
+    static_assert(sizeof...(Types) > 0, "Template parameter type list of variant can not be empty.");
+    static_assert(!detail::disjunction<std::is_reference<Types>...>::value, "Variant can not hold reference types. Maybe use std::reference_wrapper?");
+    static_assert(!detail::disjunction<std::is_array<Types>...>::value, "Variant can not hold array types.");
+    static_assert(sizeof...(Types) < std::numeric_limits<type_index_t>::max(), "Internal index type must be able to accommodate all alternatives.");
+private:
+    static const std::size_t data_size = detail::static_max<sizeof(Types)...>::value;
+    static const std::size_t data_align = detail::static_max<alignof(Types)...>::value;
+public:
+    struct adapted_variant_tag;
+    using types = std::tuple<Types...>;
+private:
+    using first_type = typename std::tuple_element<0, types>::type;
+    using unwrap_first_type = typename detail::unwrapper<first_type>::value_type;
+    using data_type = typename std::aligned_storage<data_size, data_align>::type;
+    using helper_type = detail::variant_helper<Types...>;
+
+    template <typename V, typename T = unwrap_first_type>
+        using alternative_ref = typename detail::copy_cvref<V, T>::type;
+
+    type_index_t type_index;
+#ifdef __clang_analyzer__
+    data_type data {};
+#else
+    data_type data;
+#endif
+
+public:
+    VARIANT_INLINE variant() noexcept(std::is_nothrow_default_constructible<first_type>::value)
+        : type_index(sizeof...(Types)-1)
+    {
+        static_assert(std::is_default_constructible<first_type>::value, "First type in variant must be default constructible to allow default construction of variant.");
+        new (&data) first_type();
+    }
+
+    VARIANT_INLINE variant(no_init) noexcept
+        : type_index(detail::invalid_value) {}
+
+    // http://isocpp.org/blog/2012/11/universal-references-in-c11-scott-meyers
+    template <typename T, typename Traits = detail::value_traits<T, Types...>,
+              typename Enable = typename std::enable_if<Traits::is_valid && !std::is_same<variant<Types...>, typename Traits::value_type>::value>::type >
+    VARIANT_INLINE variant(T&& val) noexcept(std::is_nothrow_constructible<typename Traits::target_type, T&&>::value)
+        : type_index(Traits::index)
+    {
+        new (&data) typename Traits::target_type(std::forward<T>(val));
+    }
+
+    VARIANT_INLINE variant(variant<Types...> const& old)
+        : type_index(old.type_index)
+    {
+        helper_type::copy(old.type_index, &old.data, &data);
+    }
+
+    VARIANT_INLINE variant(variant<Types...>&& old)
+        noexcept(detail::conjunction<std::is_nothrow_move_constructible<Types>...>::value)
+        : type_index(old.type_index)
+    {
+        helper_type::move(old.type_index, &old.data, &data);
+    }
+
+private:
+    VARIANT_INLINE void copy_assign(variant<Types...> const& rhs)
+    {
+        helper_type::destroy(type_index, &data);
+        type_index = detail::invalid_value;
+        helper_type::copy(rhs.type_index, &rhs.data, &data);
+        type_index = rhs.type_index;
+    }
+
+    VARIANT_INLINE void move_assign(variant<Types...>&& rhs)
+    {
+        helper_type::destroy(type_index, &data);
+        type_index = detail::invalid_value;
+        helper_type::move(rhs.type_index, &rhs.data, &data);
+        type_index = rhs.type_index;
+    }
+
+public:
+    VARIANT_INLINE variant<Types...>& operator=(variant<Types...>&& other)
+        // note we check for nothrow-constructible, not nothrow-assignable, since
+        // move_assign uses move-construction via placement new.
+        noexcept(detail::conjunction<std::is_nothrow_move_constructible<Types>...>::value)
+    {
+        if (this == &other) { // playing safe in release mode, hit assertion in debug.
+            assert(false);
+            return *this;
+        }
+        move_assign(std::move(other));
+        return *this;
+    }
+
+    VARIANT_INLINE variant<Types...>& operator=(variant<Types...> const& other)
+    {
+        if (this != &other)
+            copy_assign(other);
+        return *this;
+    }
+
+    // conversions
+    // move-assign
+    template <typename T, typename Traits = detail::value_traits<T, Types...>,
+              typename Enable = typename std::enable_if<Traits::is_valid && !std::is_same<variant<Types...>, typename Traits::value_type>::value>::type >
+    VARIANT_INLINE variant<Types...>& operator=(T&& rhs)
+        // not that we check is_nothrow_constructible<T>, not is_nothrow_move_assignable<T>,
+        // since we construct a temporary
+        noexcept(std::is_nothrow_constructible<typename Traits::target_type, T&&>::value
+                 && std::is_nothrow_move_assignable<variant<Types...>>::value)
+    {
+        variant<Types...> temp(std::forward<T>(rhs));
+        move_assign(std::move(temp));
+        return *this;
+    }
+
+    // copy-assign
+    template <typename T>
+    VARIANT_INLINE variant<Types...>& operator=(T const& rhs)
+    {
+        variant<Types...> temp(rhs);
+        copy_assign(temp);
+        return *this;
+    }
+
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<T, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE bool is() const
+    {
+        return type_index == detail::direct_type<T, Types...>::index;
+    }
+
+    template <typename T,typename std::enable_if<
+                         (detail::direct_type<recursive_wrapper<T>, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE bool is() const
+    {
+        return type_index == detail::direct_type<recursive_wrapper<T>, Types...>::index;
+    }
+
+    VARIANT_INLINE bool valid() const
+    {
+        return type_index != detail::invalid_value;
+    }
+
+    template <typename T, typename... Args>
+    VARIANT_INLINE void set(Args&&... args)
+    {
+        helper_type::destroy(type_index, &data);
+        type_index = detail::invalid_value;
+        new (&data) T(std::forward<Args>(args)...);
+        type_index = detail::direct_type<T, Types...>::index;
+    }
+
+    // get_unchecked<T>()
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<T, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE T& get_unchecked()
+    {
+        return *reinterpret_cast<T*>(&data);
+    }
+
+#ifdef HAS_EXCEPTIONS
+    // get<T>()
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<T, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE T& get()
+    {
+        if (type_index == detail::direct_type<T, Types...>::index)
+        {
+            return *reinterpret_cast<T*>(&data);
+        }
+        else
+        {
+            throw bad_variant_access("in get<T>()");
+        }
+    }
+#endif
+
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<T, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE T const& get_unchecked() const
+    {
+        return *reinterpret_cast<T const*>(&data);
+    }
+
+#ifdef HAS_EXCEPTIONS
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<T, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE T const& get() const
+    {
+        if (type_index == detail::direct_type<T, Types...>::index)
+        {
+            return *reinterpret_cast<T const*>(&data);
+        }
+        else
+        {
+            throw bad_variant_access("in get<T>()");
+        }
+    }
+#endif
+
+    // get_unchecked<T>() - T stored as recursive_wrapper<T>
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<recursive_wrapper<T>, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE T& get_unchecked()
+    {
+        return (*reinterpret_cast<recursive_wrapper<T>*>(&data)).get();
+    }
+
+#ifdef HAS_EXCEPTIONS
+    // get<T>() - T stored as recursive_wrapper<T>
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<recursive_wrapper<T>, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE T& get()
+    {
+        if (type_index == detail::direct_type<recursive_wrapper<T>, Types...>::index)
+        {
+            return (*reinterpret_cast<recursive_wrapper<T>*>(&data)).get();
+        }
+        else
+        {
+            throw bad_variant_access("in get<T>()");
+        }
+    }
+#endif
+
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<recursive_wrapper<T>, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE T const& get_unchecked() const
+    {
+        return (*reinterpret_cast<recursive_wrapper<T> const*>(&data)).get();
+    }
+
+#ifdef HAS_EXCEPTIONS
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<recursive_wrapper<T>, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE T const& get() const
+    {
+        if (type_index == detail::direct_type<recursive_wrapper<T>, Types...>::index)
+        {
+            return (*reinterpret_cast<recursive_wrapper<T> const*>(&data)).get();
+        }
+        else
+        {
+            throw bad_variant_access("in get<T>()");
+        }
+    }
+#endif
+
+    // get_unchecked<T>() - T stored as std::reference_wrapper<T>
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<std::reference_wrapper<T>, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE T& get_unchecked()
+    {
+        return (*reinterpret_cast<std::reference_wrapper<T>*>(&data)).get();
+    }
+
+#ifdef HAS_EXCEPTIONS
+    // get<T>() - T stored as std::reference_wrapper<T>
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<std::reference_wrapper<T>, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE T& get()
+    {
+        if (type_index == detail::direct_type<std::reference_wrapper<T>, Types...>::index)
+        {
+            return (*reinterpret_cast<std::reference_wrapper<T>*>(&data)).get();
+        }
+        else
+        {
+            throw bad_variant_access("in get<T>()");
+        }
+    }
+#endif
+
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<std::reference_wrapper<T const>, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE T const& get_unchecked() const
+    {
+        return (*reinterpret_cast<std::reference_wrapper<T const> const*>(&data)).get();
+    }
+
+#ifdef HAS_EXCEPTIONS
+    template <typename T, typename std::enable_if<
+                          (detail::direct_type<std::reference_wrapper<T const>, Types...>::index != detail::invalid_value)>::type* = nullptr>
+    VARIANT_INLINE T const& get() const
+    {
+        if (type_index == detail::direct_type<std::reference_wrapper<T const>, Types...>::index)
+        {
+            return (*reinterpret_cast<std::reference_wrapper<T const> const*>(&data)).get();
+        }
+        else
+        {
+            throw bad_variant_access("in get<T>()");
+        }
+    }
+#endif
+
+    // This function is deprecated because it returns an internal index field.
+    // Use which() instead.
+    MAPBOX_VARIANT_DEPRECATED VARIANT_INLINE type_index_t get_type_index() const
+    {
+        return type_index;
+    }
+
+    VARIANT_INLINE int which() const noexcept
+    {
+        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 T0 = alternative_ref<V>,
+              typename R = detail::result_of_unary_visit<F, T0>>
+    VARIANT_INLINE static R visit(V&& v, F&& f)
+    {
+        return detail::dispatcher<R, Types...>::apply(std::forward<V>(v), std::forward<F>(f));
+    }
+
+    // binary
+    template <typename F, typename V, typename T0 = alternative_ref<V>,
+              typename R = detail::result_of_binary_visit<F, T0>>
+    VARIANT_INLINE static R binary_visit(V&& v0, V&& v1, F&& f)
+    {
+        return detail::binary_dispatcher<R, Types...>::apply(std::forward<V>(v0),
+                                                             std::forward<V>(v1),
+                                                             std::forward<F>(f));
+    }
+
+    // match
+    // unary
+    template <typename... Fs>
+    auto VARIANT_INLINE match(Fs&&... fs) const&
+        -> decltype(variant::visit(*this, ::mapbox::util::make_visitor(std::forward<Fs>(fs)...)))
+    {
+        return variant::visit(*this, ::mapbox::util::make_visitor(std::forward<Fs>(fs)...));
+    }
+    // non-const
+    template <typename... Fs>
+    auto VARIANT_INLINE match(Fs&&... fs) &
+        -> decltype(variant::visit(*this, ::mapbox::util::make_visitor(std::forward<Fs>(fs)...)))
+    {
+        return variant::visit(*this, ::mapbox::util::make_visitor(std::forward<Fs>(fs)...));
+    }
+    template <typename... Fs>
+    auto VARIANT_INLINE match(Fs&&... fs) &&
+        -> decltype(variant::visit(std::move(*this), ::mapbox::util::make_visitor(std::forward<Fs>(fs)...)))
+    {
+        return variant::visit(std::move(*this), ::mapbox::util::make_visitor(std::forward<Fs>(fs)...));
+    }
+
+    ~variant() noexcept // no-throw destructor
+    {
+        helper_type::destroy(type_index, &data);
+    }
+
+    // comparison operators
+    // equality
+    VARIANT_INLINE bool operator==(variant const& rhs) const
+    {
+        assert(valid() && rhs.valid());
+        if (this->which() != rhs.which())
+        {
+            return false;
+        }
+        detail::comparer<variant, detail::equal_comp> visitor(*this);
+        return visit(rhs, visitor);
+    }
+
+    VARIANT_INLINE bool operator!=(variant const& rhs) const
+    {
+        return !(*this == rhs);
+    }
+
+    // less than
+    VARIANT_INLINE bool operator<(variant const& rhs) const
+    {
+        assert(valid() && rhs.valid());
+        if (this->which() != rhs.which())
+        {
+            return this->which() < rhs.which();
+        }
+        detail::comparer<variant, detail::less_comp> visitor(*this);
+        return visit(rhs, visitor);
+    }
+    VARIANT_INLINE bool operator>(variant const& rhs) const
+    {
+        return rhs < *this;
+    }
+    VARIANT_INLINE bool operator<=(variant const& rhs) const
+    {
+        return !(*this > rhs);
+    }
+    VARIANT_INLINE bool operator>=(variant const& rhs) const
+    {
+        return !(*this < rhs);
+    }
+};
+
+// unary visitor interface
+template <typename F, typename V>
+auto VARIANT_INLINE apply_visitor(F&& f, V&& v)
+    -> decltype(v.visit(std::forward<V>(v), std::forward<F>(f)))
+{
+    return v.visit(std::forward<V>(v), std::forward<F>(f));
+}
+
+// binary visitor interface
+template <typename F, typename V>
+auto VARIANT_INLINE apply_visitor(F&& f, V&& v0, V&& v1)
+    -> decltype(v0.binary_visit(std::forward<V>(v0), std::forward<V>(v1), std::forward<F>(f)))
+{
+    return v0.binary_visit(std::forward<V>(v0), std::forward<V>(v1), std::forward<F>(f));
+}
+
+// getter interface
+
+#ifdef HAS_EXCEPTIONS
+template <typename ResultType, typename T>
+auto get(T& var)->decltype(var.template get<ResultType>())
+{
+    return var.template get<ResultType>();
+}
+#endif
+
+template <typename ResultType, typename T>
+ResultType& get_unchecked(T& var)
+{
+    return var.template get_unchecked<ResultType>();
+}
+
+#ifdef HAS_EXCEPTIONS
+template <typename ResultType, typename T>
+auto get(T const& var)->decltype(var.template get<ResultType>())
+{
+    return var.template get<ResultType>();
+}
+#endif
+
+template <typename ResultType, typename T>
+ResultType const& get_unchecked(T const& var)
+{
+    return var.template get_unchecked<ResultType>();
+}
+// variant_size
+template <typename T>
+struct variant_size;
+
+//variable templates is c++14
+//template <typename T>
+//constexpr std::size_t variant_size_v = variant_size<T>::value;
+
+template <typename T>
+struct variant_size<const T>
+    : variant_size<T> {};
+
+template <typename T>
+struct variant_size<volatile T>
+    : variant_size<T> {};
+
+template <typename T>
+struct variant_size<const volatile T>
+    : variant_size<T> {};
+
+template <typename... Types>
+struct variant_size<variant<Types...>>
+    : std::integral_constant<std::size_t, sizeof...(Types)> {};
+
+// variant_alternative
+template <std::size_t Index, typename T>
+struct variant_alternative;
+
+#if defined(__clang__)
+#if __has_builtin(__type_pack_element)
+#define has_type_pack_element
+#endif
+#endif
+
+#if defined(has_type_pack_element)
+template <std::size_t Index, typename ...Types>
+struct variant_alternative<Index, variant<Types...>>
+{
+    static_assert(sizeof...(Types) > Index , "Index out of range");
+    using type = __type_pack_element<Index, Types...>;
+};
+#else
+template <std::size_t Index, typename First, typename...Types>
+struct variant_alternative<Index, variant<First, Types...>>
+    : variant_alternative<Index - 1, variant<Types...>>
+{
+    static_assert(sizeof...(Types) > Index -1 , "Index out of range");
+};
+
+template <typename First, typename...Types>
+struct variant_alternative<0, variant<First, Types...>>
+{
+    using type = First;
+};
+
+#endif
+
+template <size_t Index, typename T>
+using variant_alternative_t = typename variant_alternative<Index, T>::type;
+
+template <size_t Index, typename T>
+struct variant_alternative<Index, const T>
+    : std::add_const<variant_alternative<Index, T>> {};
+
+template <size_t Index, typename T>
+struct variant_alternative<Index, volatile T>
+    : std::add_volatile<variant_alternative<Index, T>> {};
+
+template <size_t Index, typename T>
+struct variant_alternative<Index, const volatile T>
+    : std::add_cv<variant_alternative<Index, T>> {};
+
+} // namespace util
+} // namespace mapbox
+
+// hashable iff underlying types are hashable
+namespace std {
+template <typename... Types>
+struct hash< ::mapbox::util::variant<Types...>> {
+    std::size_t operator()(const ::mapbox::util::variant<Types...>& v) const noexcept
+    {
+        return ::mapbox::util::apply_visitor(::mapbox::util::detail::hasher{}, v);
+    }
+};
+
+}
+
+#endif // MAPBOX_UTIL_VARIANT_HPP
diff --git a/src/mapbox/variant_cast.hpp b/src/mapbox/variant_cast.hpp
new file mode 100644
index 0000000..fe1ab35
--- /dev/null
+++ b/src/mapbox/variant_cast.hpp
@@ -0,0 +1,85 @@
+#ifndef VARIANT_CAST_HPP
+#define VARIANT_CAST_HPP
+
+#include <type_traits>
+
+namespace mapbox {
+namespace util {
+
+namespace detail {
+
+template <class T>
+class static_caster
+{
+public:
+    template <class V>
+    T& operator()(V& v) const
+    {
+        return static_cast<T&>(v);
+    }
+};
+
+template <class T>
+class dynamic_caster
+{
+public:
+    using result_type = T&;
+    template <class V>
+    T& operator()(V& v, typename std::enable_if<!std::is_polymorphic<V>::value>::type* = nullptr) const
+    {
+        throw std::bad_cast();
+    }
+    template <class V>
+    T& operator()(V& v, typename std::enable_if<std::is_polymorphic<V>::value>::type* = nullptr) const
+    {
+        return dynamic_cast<T&>(v);
+    }
+};
+
+template <class T>
+class dynamic_caster<T*>
+{
+public:
+    using result_type = T*;
+    template <class V>
+    T* operator()(V& v, typename std::enable_if<!std::is_polymorphic<V>::value>::type* = nullptr) const
+    {
+        return nullptr;
+    }
+    template <class V>
+    T* operator()(V& v, typename std::enable_if<std::is_polymorphic<V>::value>::type* = nullptr) const
+    {
+        return dynamic_cast<T*>(&v);
+    }
+};
+}
+
+template <class T, class V>
+typename detail::dynamic_caster<T>::result_type
+dynamic_variant_cast(V& v)
+{
+    return mapbox::util::apply_visitor(detail::dynamic_caster<T>(), v);
+}
+
+template <class T, class V>
+typename detail::dynamic_caster<const T>::result_type
+dynamic_variant_cast(const V& v)
+{
+    return mapbox::util::apply_visitor(detail::dynamic_caster<const T>(), v);
+}
+
+template <class T, class V>
+T& static_variant_cast(V& v)
+{
+    return mapbox::util::apply_visitor(detail::static_caster<T>(), v);
+}
+
+template <class T, class V>
+const T& static_variant_cast(const V& v)
+{
+    return mapbox::util::apply_visitor(detail::static_caster<const T>(), v);
+}
+}
+}
+
+#endif // VARIANT_CAST_HPP
diff --git a/src/mapbox/variant_io.hpp b/src/mapbox/variant_io.hpp
new file mode 100644
index 0000000..1456cc5
--- /dev/null
+++ b/src/mapbox/variant_io.hpp
@@ -0,0 +1,45 @@
+#ifndef MAPBOX_UTIL_VARIANT_IO_HPP
+#define MAPBOX_UTIL_VARIANT_IO_HPP
+
+#include <iosfwd>
+
+#include <mapbox/variant.hpp>
+
+namespace mapbox {
+namespace util {
+
+namespace detail {
+// operator<< helper
+template <typename Out>
+class printer
+{
+public:
+    explicit printer(Out& out)
+        : out_(out) {}
+    printer& operator=(printer const&) = delete;
+
+    // visitor
+    template <typename T>
+    void operator()(T const& operand) const
+    {
+        out_ << operand;
+    }
+
+private:
+    Out& out_;
+};
+}
+
+// operator<<
+template <typename CharT, typename Traits, typename... Types>
+VARIANT_INLINE std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& out, variant<Types...> const& rhs)
+{
+    detail::printer<std::basic_ostream<CharT, Traits>> visitor(out);
+    apply_visitor(visitor, rhs);
+    return out;
+}
+} // namespace util
+} // namespace mapbox
+
+#endif // MAPBOX_UTIL_VARIANT_IO_HPP
diff --git a/src/mapbox/variant_visitor.hpp b/src/mapbox/variant_visitor.hpp
new file mode 100644
index 0000000..54ddba0
--- /dev/null
+++ b/src/mapbox/variant_visitor.hpp
@@ -0,0 +1,43 @@
+#ifndef MAPBOX_UTIL_VARIANT_VISITOR_HPP
+#define MAPBOX_UTIL_VARIANT_VISITOR_HPP
+
+#include <utility>
+
+namespace mapbox {
+namespace util {
+
+template <typename... Fns>
+struct visitor;
+
+template <typename Fn>
+struct visitor<Fn> : Fn
+{
+    using Fn::operator();
+
+    template<typename T>
+    visitor(T&& fn) : Fn(std::forward<T>(fn)) {}    
+};
+
+template <typename Fn, typename... Fns>
+struct visitor<Fn, Fns...> : Fn, visitor<Fns...>
+{
+    using Fn::operator();
+    using visitor<Fns...>::operator();
+
+    template<typename T, typename... Ts>
+    visitor(T&& fn, Ts&&... fns)
+        : Fn(std::forward<T>(fn))
+        , visitor<Fns...>(std::forward<Ts>(fns)...) {}
+};
+
+template <typename... Fns>
+visitor<typename std::decay<Fns>::type...> make_visitor(Fns&&... fns)
+{
+    return visitor<typename std::decay<Fns>::type...>
+        (std::forward<Fns>(fns)...);
+}
+    
+} // namespace util
+} // namespace mapbox
+
+#endif // MAPBOX_UTIL_VARIANT_VISITOR_HPP