In this post, we continue discovering the changes introduced by C++23. We are going to look into three (and a half) small changes, each affecting constructors of some standard library types. We’re going to see how new constructors for container types, a new range constructor for string_view and some default template arguments for pair.

C++23: More Small Changes

by Sandor Dargo

From the article:

As of C++20, almost all container-like objects (containers and container-adaptors) can be initialized with a pair of iterators.

std::vector<int> v{42, 51, 66};
std::list<int> l(v.begin(), v.end());

All of them, except for std::stack and std::queue. They don’t provide such overloads. If you want to initialize them with a pair of iterators, you need an intermediary std::initiailizer_list.

std::vector<int> v{42, 51, 66};
// std::queue<int> q1(v.begin(), v.end()); // DOESN'T COMPILE!
std::queue<int> q2({v.begin(), v.end()});

This inconsistency, at first, looks like a small inconvenience. But its effects are much deeper. While using the stack or queue on its own is not a big burden, if you want to offer functionality that works with all container-like objects, you have a higher price to pay.

Due to the lack of an iterator-pair-based constructor, you either have to ...