#include <algorithm>#include <array>#include <cassert>#include <cstddef>#include <iostream>#include <span>#include <string_view> void print(std::string_view info="",std::span<constint> span={},std::size_t extent=0,std::size_t size_of=0){if(span.empty()){std::cout<< info<<'\n';return;} std::cout<< info<<'['<< span.size()<<"] {";    std::ranges::for_each(span,[](constint x){std::cout<<' '<< x;});std::cout<<" }"; if(extent){std::cout<<" extent = ";if(extent==std::dynamic_extent)std::cout<<"dynamic";elsestd::cout<< extent;} if(size_of)std::cout<<", sizeof = "<< size_of; std::cout<<'\n';} int main(){std::array<int,6> a1;std::array<int,6> a2;    a1.fill(3);    a2.fill(4); auto s1=std::span(a1);auto s2=std::span(a2);    print("s1", s1, s1.extent, sizeof(s1));    print("s2", s2, s2.extent, sizeof(s2)); // Check that assignment performs a shallow copy.    s1= s2;(s1.data()== s2.data()&& s1.size()== s2.size())? print("s1 = s2; is a shallow copy!"): print("s1 = s2; is a deep copy!");    print("s1", s1);     print("Fill s1 with 5:");    std::ranges::fill(s1,5);// s2 is also 'updated' since s1 and s2 point to the same dataassert(std::ranges::equal(s1, s2));    print("s1", s1);    print("s2", s2);    print(); int a3[]{1,2,3,4};int a4[]{2,3,4,5};int a5[]{3,4,5}; std::span<int,std::dynamic_extent> dynamic_1{a3};std::span<int,std::dynamic_extent> dynamic_2{a4,3};std::span<int,4> static_1{a3};std::span<int,4> static_2{a4};std::span<int,3> static_3{a5};     print("dynamic_1", dynamic_1, dynamic_1.extent, sizeof(dynamic_1));    print("dynamic_2", dynamic_2, dynamic_2.extent, sizeof(dynamic_2));    print("static_1", static_1, static_1.extent, sizeof(static_1));    print("static_2", static_2, static_2.extent, sizeof(static_2));    print("static_3", static_3, static_3.extent, sizeof(static_3));     dynamic_1= dynamic_2;// OK    dynamic_1= static_1;// OK//  static_1 = dynamic_1;  // ERROR: no match for ‘operator=’    static_1= static_2;// OK: same extents = 4//  static_1 = static_3;   // ERROR: different extents: 4 and 3}

s1[6] { 3 3 3 3 3 3 } extent = 6, sizeof = 8s2[6] { 4 4 4 4 4 4 } extent = 6, sizeof = 8s1 = s2; is a shallow copy!s1[6] { 4 4 4 4 4 4 }Fill s1 with 5:s1[6] { 5 5 5 5 5 5 }s2[6] { 5 5 5 5 5 5 } dynamic_1[4] { 1 2 3 4 } extent = dynamic, sizeof = 16dynamic_2[3] { 2 3 4 } extent = dynamic, sizeof = 16static_1[4] { 1 2 3 4 } extent = 4, sizeof = 8static_2[4] { 2 3 4 5 } extent = 4, sizeof = 8static_3[3] { 3 4 5 } extent = 3, sizeof = 8