std::span size() method

since C++20

constexpr size_type size() const noexcept;

Returns the number of elements in the span, i.e. std::distance(begin(), end()).

Parameters

(none)

Return value

The number of elements in the span.

Complexity

Constant - O(1).

Notes

Feature testing macro: __cpp_lib_ssize.

Example

Main.cpp

#include <iostream>
#include <span>
 
void show_sizes(std::span<const int> span)
{
    std::cout
        << span                 .size() << ' ' // 8
        << span.first(7)        .size() << ' ' // 7
        << span.first<6>()      .size() << ' ' // 6 
        << span.last(5)         .size() << ' ' // 5 
        << span.last<4>()       .size() << ' ' // 4
        << span.subspan(2, 3)   .size() << ' ' // 3 
        << span.subspan<3, 2>() .size() << ' ' // 2
        << '\n';
}
 
int main()
{
    int antique_array[] { 1, 2, 3, 4, 5, 6, 7, 8 };
    show_sizes(antique_array);
}

Possible output

8 7 6 5 4 3 2