NAME¶

std::span::operator[] - std::span::operator[]

Synopsis¶

constexpr reference operator[]( size_type idx ) const; (since C++20)

Returns a reference to the idx^th element of the sequence. The behavior is undefined
if idx is out of range (i.e., if it is greater than or equal to size()).

Parameters¶

idx - the index of the element to access

Return value¶

A reference to the idx^th element of the sequence, i.e., data()[idx].

Exceptions¶

Throws nothing.

Example¶

// Run this code

#include <cstddef>
#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

See also¶

at access specified element with bounds checking
(C++26) (public member function)
data direct access to the underlying contiguous storage
(public member function)
size returns the number of elements
(public member function)
as_bytes converts a span into a view of its underlying bytes
as_writable_bytes (function template)
(C++20)