#include <iostream>
#include <vector>
#include <stdlib.h>
 
using namespace std;
 
void multiply_by_2(vector<double> &v)
{
  int i;
  int n = v.size();
 
  // multiply each coordinate by 2
 
  for (i=0; i<n; i++)
    v[i] *= 2;
}
 
int main()
{
   int i;
   int n=10;
   vector<double> v(n);
 
   srand48(123);
 
   for (i=0; i<n; i++)
     v[i] = drand48();
 
   cout << "old vector:" << endl;
   for (i=0; i<n; i++)
     cout << v[i] << endl;
 
   multiply_by_2(v);
 
   cout << "new vector:" << endl;
   for (i=0; i<n; i++)
     cout << v[i] << endl;
 
   return 0;
}

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