void update_data() {
            vector_listbox->Items->Clear(); // clearing the elements
            list_listbox->Items->Clear();

            if (GL_SHOW_FULL_ARRAYS) // ensure if we want to see full version (takes longer to render)
            {
                if (GL_VECTOR.size() == 0) vector_listbox->Items->Insert(vector_listbox->Items->Count, "empty");       // for vector full
                else for (auto el : GL_VECTOR)  vector_listbox->Items->Insert(vector_listbox->Items->Count, cs(el));

                if (GL_LIST.size() == 0) list_listbox->Items->Insert(list_listbox->Items->Count, "empty");             // for list full
                else for (auto el : GL_LIST)  list_listbox->Items->Insert(list_listbox->Items->Count, cs(el));
            }
            else // if we using partial representation of arrays
            {
                if (GL_VECTOR.size() == 0) vector_listbox->Items->Insert(vector_listbox->Items->Count, "empty");             // for vector
                else {
                    for (size_t i = 0; i < GL_SHOWN_LENGTH - 2; i++)
                        vector_listbox->Items->Insert(vector_listbox->Items->Count, cs(s(i) + ": " + s(GL_VECTOR.at(i))));
                    vector_listbox->Items->Insert(vector_listbox->Items->Count, "...");
                    vector_listbox->Items->Insert(vector_listbox->Items->Count, cs(s(GL_VECTOR.size() - 1) + ": " + s(GL_VECTOR.back())));
                }

                if (GL_LIST.size() == 0) list_listbox->Items->Insert(list_listbox->Items->Count, "empty");             // for list
                else {
                    auto it = GL_LIST.begin();
                    for (size_t i = 0; i < GL_SHOWN_LENGTH - 2; i++)
                        list_listbox->Items->Insert(list_listbox->Items->Count, cs(s(i) + ": " + s(*it++)));
                    list_listbox->Items->Insert(list_listbox->Items->Count, "...");
                    list_listbox->Items->Insert(list_listbox->Items->Count, cs(s(GL_LIST.size() - 1) + ": " + s(GL_LIST.back())));
                }
            }
            dh("data updated");
        }