#include <iostream>#include <ranges>#include <vector> template<std::ranges::input_range R>void print(char id, R&& r){if(std::ranges::empty(r)){std::cout<<'\t'<< id<<") Empty\n";return;} std::cout<<'\t'<< id<<") Elements:";for(constauto& element: r)std::cout<<' '<< element;std::cout<<'\n';} int main(){{auto v=std::vector<int>{1,2,3};std::cout<<"(1) ranges::empty uses std::vector::empty:\n";        print('a', v);         v.clear();        print('b', v);}{std::cout<<"(2) ranges::empty uses ranges::size(initializer_list):\n";auto il={7,8,9};        print('a', il);         print('b',std::initializer_list<int>{});}{std::cout<<"(2) ranges::empty on a raw array uses ranges::size:\n";int array[]={4,5,6};// array has a known bound        print('a', array);}{struct Scanty:privatestd::vector<int>{usingstd::vector<int>::begin;usingstd::vector<int>::end;usingstd::vector<int>::push_back;// Note: both empty() and size() are hidden}; std::cout<<"(3) calling ranges::empty on an object w/o empty() or size():\n";        Scanty y;        print('a', y);        y.push_back(42);        print('b', y);}}

(1) ranges::empty uses std::vector::empty:        a) Elements: 1 2 3        b) Empty(2) ranges::empty uses ranges::size(initializer_list):        a) Elements: 7 8 9        b) Empty(2) ranges::empty on a raw array uses ranges::size:        a) Elements: 4 5 6(3) calling ranges::empty on an object w/o empty() or size():        a) Empty        b) Elements: 42