Creating a Span from a Vector

You can create a std::span from a std::vector by passing the vector to the std::span constructor. Here's an example:

1#include <iostream>
2#include <span>
3#include <vector>
4
5void PrintSpan(std::span<const int> data) {
6  for (int i : data) {
7    std::cout << i << " ";
8  }
9  std::cout << "\n";
10}
11
12int main() {
13  std::vector<int> vec{1, 2, 3, 4, 5};
14  std::span<int> span{vec};  
15
16  PrintSpan(span);
17}

11 2 3 4 5

In this example, we create a std::vector<int> called vec with some initial values. We then create a std::span<int> called span by passing vec to its constructor.

We can pass span to functions that expect a std::span, like PrintSpan in this example. PrintSpan takes a std::span<const int>, which allows it to read the elements but not modify them.

Note that the std::span does not own the data. If the original std::vector goes out of scope or is modified, the std::span will be affected.

Also, if you have a const std::vector, you should create a std::span<const T> to avoid any accidental modifications:

1const std::vector<int> vec{1, 2, 3, 4, 5};
2std::span<const int> span{vec};

This way, the constness of the original vector is carried over to the span.