added implementation for operator=

Function.hpp

@@ -16,11 +16,23 @@ private:
     class callable : public callable_base
     {
     private:
-        Fun _f;
+        Fun _fun;
     public:
-        callable(Fun f):_f(f) {}
+        callable(Fun fun):_fun(fun) {}
         virtual Ret call(Args... args)
-        { return _f(std::forward<Args>(args)...); }
+        { return _fun(std::forward<Args>(args)...); }
     };
+
+    callable_base* _fun;
 public:
+    Function() {}
+
+    template <typename Fun>
+    Function& operator=(Fun fun)
+    {
+        _fun = new callable<Fun>(fun);
+        return *this;
+    }
+
+    ~Function() { delete _fun; }
 };