diff --git a/source/mijin/types/script_value.hpp b/source/mijin/types/script_value.hpp
index 869ca36..96933ee 100644
--- a/source/mijin/types/script_value.hpp
+++ b/source/mijin/types/script_value.hpp
@@ -6,6 +6,7 @@
 
 #include <charconv>
 #include <string>
+#include <unordered_map>
 #include <variant>
 #include <vector>
 
@@ -14,6 +15,16 @@
 
 namespace mijin
 {
+//
+// public traits
+//
+
+template<typename TSearch, typename TVariant>
+inline constexpr bool variant_contains_v = false;
+
+template<typename TSearch, typename... TVariantTypes>
+inline constexpr bool variant_contains_v<TSearch, std::variant<TVariantTypes...>> = mijin::is_any_type_v<TSearch, TVariantTypes...>;
+
 //
 // public types
 //
@@ -26,12 +37,12 @@ template<typename TScriptValue>
 struct ArrayValue
 {
     std::vector<TScriptValue> values;
+};
 
-    bool operator==(const ArrayValue& other) const;
-    inline bool operator!=(const ArrayValue& other) const {
-        return !(*this == other);
-    }
-    std::partial_ordering operator<=>(const ArrayValue& other) const;
+template<typename TScriptValue>
+struct MapValue
+{
+    std::unordered_map<std::string, TScriptValue> values;
 };
 
 struct UndefinedValue
@@ -52,6 +63,7 @@ using script_value_base_t = std::variant<
     script_float_t,
     std::string,
     ArrayValue<TConcrete>,
+    MapValue<TConcrete>,
     TAdditional...
 >;
 
@@ -62,8 +74,12 @@ public:
     using base_t = script_value_base_t<TConcrete, TAdditional...>;
     using concrete_t = TConcrete;
     using array_t = ArrayValue<TConcrete>;
+    using map_t = MapValue<TConcrete>;
+
+    template<typename T>
+    static constexpr bool can_hold_type_v = variant_contains_v<std::remove_cv_t<T>, base_t> || std::is_arithmetic_v<T>;
 private:
-    base_t base_;
+    base_t base_ = UndefinedValue();
 public:
     ScriptValue() noexcept = default;
     ScriptValue(const ScriptValue&) noexcept = default;
@@ -79,16 +95,7 @@ public:
     template<typename TFunction>
     auto visit(TFunction&& function) const
     {
-        using result_t = std::invoke_result_t<TFunction, long long>;
-
-        if constexpr (std::is_same_v<result_t, void>)
-        {
-            std::visit(function, base_);
-        }
-        else
-        {
-            return std::visit(function, base_);
-        }
+        return std::visit(function, base_);
     }
 
     [[nodiscard]]
@@ -203,7 +210,8 @@ public:
         {
             return *static_cast<copy_cv_t<std::remove_reference_t<decltype(*this)>, TConcrete>*>(this);
         }
-        else if constexpr (is_any_type_v<T, TAdditional...>)
+        else if constexpr (std::is_same_v<type_t, array_t> || std::is_same_v<type_t, map_t>
+                || is_any_type_v<T, TAdditional...>)
         {
             if (std::holds_alternative<T>(base_))
             {