#include <vector>
#include <iostream>
 
struct A
{
    std::vector<int> seq ;
 
    std::vector<int> get_copy_of_seq() const { return seq ; }
 
    std::vector<int>& get_reference_to_seq() { return seq ; }
};
 
int main()
{
    A a ;
 
    auto val = a.get_copy_of_seq() ;
    auto& ref = a.get_reference_to_seq() ;
 
    std::cout << val.size() << '\n' ; // 0
    std::cout << ref.size() << '\n' ; // 0
 
    a.seq.resize(1234) ;
    std::cout << val.size() << '\n' ; // 0
    std::cout << ref.size() << '\n' ; // 1234
}
 

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