int myArray[5] = {1, 2, 3, 4, 5};
 for (auto& c : myArray) c *= 2;
 for (auto c: myArray) std::cout << c << " ";   // 2 4 6 8 10

 std::vector<int> vecInt({1, 2, 3, 4, 5});
 for (auto& c: vecInt) c *= 2;
 for (auto c: vecInt) std::cout << c << " ";    // 2 4 6 8 10

 std::string str= {"Only for Testing Purpose."};
 for (auto& c: str) c=std::toupper(c);
 for (char c: str) std::cout << c;         // ONLY FOR TESTING PURPOSE.

 str= {"Only for Testing Purpose."};
 for (autor& c: str) c=std::isupper(c)? std::tolower(c): std::toupper(c);
 for (auto c: str) std::cout << c;         // oNLY FOR tESTING pURPOSE