diff --git a/a8/lisp.cc b/a8/lisp.cc
index 1f5cbc2..055fe13 100644
--- a/a8/lisp.cc
+++ b/a8/lisp.cc
@@ -43,14 +43,46 @@ namespace a8
             vars_[name] = std::make_shared<Value>(proc);
         }
 
-        bool Expr::Compile(const std::string& script, std::shared_ptr<Scope> scope)
+        std::shared_ptr<Value> Expr::Compile(const std::string& script, std::shared_ptr<Scope> scope)
         {
 
         }
 
-        std::vector<std::shared_ptr<const Value>> Expr::Eval(std::shared_ptr<Scope> scope)
+        std::shared_ptr<Value> Expr::Eval(std::shared_ptr<Value> x, std::shared_ptr<Scope> env)
         {
-
+            while (true) {
+                switch (x->type) {
+                case ValueType::kAtom:
+                    {
+                        return x;
+                    }
+                    break;
+                case ValueType::kSymbol:
+                    {
+                        Symbol&& symbol = std::any_cast<Symbol>(x->value);
+                        return env->Find(symbol.name);
+                    }
+                    break;
+                case ValueType::kList:
+                    {
+                        List&& list = std::any_cast<List>(x->value);
+                        auto leader = list.at(0);
+                        if (leader->type != ValueType::kCProc) {
+                            abort();
+                        }
+                        CProc&& cproc = std::any_cast<CProc>(leader->value);
+                        List exps = List(list.begin() + 1, list.end());
+                        return cproc(exps);
+                    }
+                    break;
+                default:
+                    {
+                        abort();
+                        return nullptr;
+                    }
+                    break;
+                }
+            }
         }
 
     }
diff --git a/a8/lisp.h b/a8/lisp.h
index 929b094..16a8f08 100644
--- a/a8/lisp.h
+++ b/a8/lisp.h
@@ -21,7 +21,7 @@ namespace a8
         };
         struct Value;
         typedef std::vector<std::shared_ptr<Value>> List;
-        typedef std::function<const List(const List)> CProc;
+        typedef std::function<std::shared_ptr<Value>(const List)> CProc;
 
         struct Atom
         {
@@ -42,6 +42,7 @@ namespace a8
             Value(List list);
             Value(Symbol symbol);
             Value(CProc cproc);
+            bool IsType(ValueType t) { return t == type; };
         };
 
         class Scope
@@ -59,15 +60,10 @@ namespace a8
         {
         public:
 
-            bool Compile(const std::string& script, std::shared_ptr<Scope> scope);
-            std::vector<std::shared_ptr<const Value>> Eval(std::shared_ptr<Scope> scope);
-
-            List GetExprList() { return list_; };
+            std::shared_ptr<Value> Compile(const std::string& script, std::shared_ptr<Scope> scope);
+            std::shared_ptr<Value> Eval(std::shared_ptr<Value> x, std::shared_ptr<Scope> env);
 
         private:
-
-            List list_;
-
         };
 
     }