std::span<T,Extent>::operator[]

 

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std::span

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span::operator=

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span::beginspan::cbegin (C++23)

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as_bytesas_writable_bytes

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dynamic_extent

Deduction guides

 

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