advanced patterns with std::deque when resizing and accessing elements in C++17
I tried several approaches but none seem to work... I'm working with an unexpected scenario with `std::deque` in C++17 when I try to resize the container and subsequently access its elements. I've defined a simple class `Data` that has a single integer member, and I'm trying to manage a deque of these objects. After resizing, I'm unable to access the elements correctly, and it appears that I'm hitting some undefined behavior, leading to incorrect values being printed. Here's a minimal example of what I'm doing: ```cpp #include <iostream> #include <deque> class Data { public: int value; Data(int val) : value(val) {} }; int main() { std::deque<Data> myDeque; myDeque.push_back(Data(1)); myDeque.push_back(Data(2)); myDeque.push_back(Data(3)); // Resize the deque to 5 myDeque.resize(5); // Trying to access all elements after resizing for (size_t i = 0; i < myDeque.size(); ++i) { std::cout << "Element " << i << ": " << myDeque[i].value << std::endl; } return 0; } ``` When I run this code, I get the output: ``` Element 0: 1 Element 1: 2 Element 2: 3 Element 3: 0 Element 4: 0 ``` I expected the newly added elements to be default-initialized and not just show up as 0. Is there something I'm missing regarding the resizing behavior of `std::deque`? I have also tried initializing the deque with default objects, but it didn't solve the question. The behavior seems inconsistent, especially when compared to `std::vector`. Any insights on how to properly handle this situation would be greatly appreciated. My development environment is Linux. Thanks in advance! For context: I'm using C++ on CentOS. Any ideas what could be causing this?