diff --git a/a8/lisp.h b/a8/lisp.h
index 9e3d67f..2f6283c 100644
--- a/a8/lisp.h
+++ b/a8/lisp.h
@@ -6,11 +6,19 @@
   列表: list
   原子: atom
  */
+
 namespace a8
 {
 
     namespace lisp
     {
+        enum class ValueType : int
+        {
+            kAtom = 1,
+            kList = 2,
+            kSymbol = 3,
+            kCProc = 4,
+        };
 
         struct List
         {
@@ -29,7 +37,8 @@ namespace a8
 
         struct Value
         {
-            int value_type = 0;
+            ValueType type;
+            std::shared_ptr<Symbol> symbol;
             std::shared_ptr<Atom> atom;
             std::shared_ptr<List> list;
         }