std::span operator[]

since C++20

constexpr reference operator[](size_type idx) const;

Returns a reference

to the element at specified index idx.

caution

No bounds checking is performed, using an element out of bounds is undefined behavior

.

Parameters

• idx - position of the character to return

Return value

Reference to the requested character.

Exceptions

(none)

Complexity

Constant - O(1).

Example

Main.cpp

#include <iostream>
#include <span>
#include <utility>
 
void reverse(std::span<int> span) {
    for (std::size_t i = 0, j = std::size(span); i < j; ++i) {
        --j;
        std::swap(span[i], span[j]);
    }
}
 
void print(std::span<const int> const span) {
    for (int element: span) {
        std::cout << element << ' ';
    }
    std::cout << '\n';
}
 
int main() {
    int data[]{ 1, 2, 3, 4, 5 };
    print(data);
    reverse(data);
    print(data);
}

Output

1 2 3 4 5 
5 4 3 2 1