C++通过引用返回值

#include <iostream>
#include <ctime>

using namespace std;

double vals[] = {10.1, 12.6, 33.1, 24.1, 50.0};

double& setValues( int i ) {
   return vals[i];   // return a reference to the ith element
}

// main function to call above defined function.
int main () {

   cout << "Value before change" << endl;
   for ( int i = 0; i < 5; i++ ) {
      cout << "vals[" << i << "] = ";
      cout << vals[i] << endl;
   }

   setValues(1) = 20.23; // change 2nd element
   setValues(3) = 70.8;  // change 4th element

   cout << "Value after change" << endl;
   for ( int i = 0; i < 5; i++ ) {
      cout << "vals[" << i << "] = ";
      cout << vals[i] << endl;
   }
   return 0;
}