std::span::size(3)

NAME
std::span::size - std::span::size

Synopsis
   constexpr size_type size() const noexcept; (since C++20)
   Returns the number of elements in the span.

Parameters
   (none)

Return value
   The number of elements in the span.

Note
   Feature-test macro Value Std Feature
   __cpp_lib_ssize 201902L (C++20) std::ssize and unsigned std::span::size

Example
// Run this code
 #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);
 }

Output:
 8 7 6 5 4 3 2

See also
   constructor constructs a span
                 (public member function)
   size_bytes returns the size of the sequence in bytes
                 (public member function)