// call by reference

 

/* p71

#include<iostream>

using std::cout;
using std::endl;

void swap(int&a , int &b)

{
 int temp=a;
 a=b;
 b=temp;
}

int main(void)
{

 int val1=10;
 int val2=20;

 cout<<"val1:"<<val1<<' ';
 cout<<"val2:"<<val2<<endl;

 swap(val1,val2);
 cout<<"val1:"<<val1<<' ';
 cout<<"val2:"<<val2<<endl;
 return 0;
}