Implements indexing, currently can only be used with strings

src/Evaluator/EvalValues/EvalValue.hpp

@@ -34,6 +34,10 @@ public:
     virtual std::string* EvaluateString(){
         throw EvaluationException("Can't evaluate this EvalValue as string.");
     }
+
+    virtual EvalValue* IndexValue(EvalValue* val){
+        throw EvaluationException("Can't index this EvalValue");
+    }
 };
 
 class BooleanEvalValue : public EvalValue{