Implements iterator for user data collection

src/Evaluator/Iterator/Iterator.hpp

@@ -10,7 +10,7 @@ using namespace std;
 namespace Porygon::Evaluation{
     class Iterator {
     public:
-        virtual EvalValue* GetCurrent() = 0;
+        virtual const  EvalValue* GetCurrent() = 0;
         virtual bool MoveNext() = 0;
         virtual void Reset() = 0;
         virtual ~Iterator(){}