#include <iostream>
#include <cmath>
#include <valarray>                 // include valarray from STL

using namespace std;

typedef valarray<double> Vector;    // define vector type

// function to print vector to screen
void print (const Vector& v)
{
  cout << "[";
  for (int i=0; i<(int)v.size(); ++i)
    cout << " " << v[i];
  cout << " ]" << endl;
}

int main ()
{
  Vector v(10);                     // create vector with 10 entries
  Vector w;                         // vector of length 0 so far

  v = 0;                            // set all entries to 0

  v[0] = 1;                         // set some of the entries
  v[3] = -2.6;                      // ATTENTION: 0-based indices
  v[5] = -3.3;                      //   entries range from v[0] to v[9]
  v[7] = 0.2;                       //   v[10] is FORBIDDEN !
  
  cout << "v = "; print (v);        // print vector to screen

  w.resize (10);                    // make w a vector with 10 entries
  w = 0;
  w[0] = 1;
  w[3] = 9;
  w[9] = -0.5;

  cout << "w = "; print (w);        // print "w"

  cout << "adding w to v..." << endl;

  v += w;                           // add w to v

  cout << "v = "; print (v);

  int n;
  do
    {
      cout << "please enter a natural number: ";
      cin >> n;
    }
  while (! (n > 0));
  
  Vector u(n);                      // create a vector with the given length

  for (int i=0; i<n; ++i)           // fill with values
    u[i] = 4.4 * i / (double)(n-1);

  cout << "here is a vector with " << n << " entries:" << endl;
  print (u);
}