// FILE ex_vector1.cc

#include <iostream>
#include <cmath>
#include <cassert>

using namespace std;



/// a vector of double entries
class MyVector
{
private:
  int size_;      // size/dimension of the vector
  double* data_;  // array of the entries
  
public:
  
  // (default) constructor
  MyVector(int size=0)
  {
    size_ = size;
    data_ = new double[size_];
  }
  
  // destructor
  ~MyVector ()
  {
    delete[] data_;
  }
  
  // copy constructor
  MyVector (const MyVector& v)
  {
    size_ = v.size_;
    data_ = new double[size_];
    memcpy (data_, v.data_, size_ * sizeof(double));
  }
  
  // assignment
  MyVector& operator= (const MyVector& v)
  {
    if (this != &v)
      {
	if (size_ != v.size_)
	  {
	    delete[] data_;
	    size_ = v.size_;
	    data_ = new double[size_];
	  }
	memcpy (data_, v.data_, size_ * sizeof(double));
      }
    return *this;
  }
  
  // get size
  int size () const { return size_; }
  
  // set size
  void setSize (int size)
  {
    if (size_ != size)
      {
	delete[] data_;
	size_ = size;
	data_ = new double[size_];
      }
  }

  // const element access
  double operator[] (int i) const
  {
    assert (0 <= i && i < size_);
    return data_[i]; 
  }
  
  // element access by reference
  double& operator[] (int i)
  {
    assert (0 <= i && i < size_);    
    return data_[i]; 
  }
  
  void scale (double factor)
  {
    for (int i=0; i<size_; ++i)
      {
	data_[i] *= factor;
      }
  }
  
  void print (ostream& os) const
  {
    os << '(';
    if (size_ > 0) os << data_[0];
    for (int i=1; i<size_; ++i) os << ", " << data_[i];
    os << ')';
  }
  
}; // class MyVector



inline
ostream& operator<< (ostream& os, const MyVector& v)
{
  v.print (os);
  return os;
}



void add (const MyVector& v, const MyVector& w, MyVector& res)
{
  assert (v.size () == w.size());
  res.setSize (v.size ());
  for (int i=0; i<v.size (); ++i)
    {
      res[i] = v[i] + w[i];
    }
}



void mult (double factor, const MyVector& v, MyVector& res)
{
  res.setSize (v.size ());
  for (int i=0; i<v.size (); ++i)
    {
      res[i] = factor * v[i];
    }
}



int main ()
{
  MyVector x(3);
  MyVector y(3);
  MyVector z;
  
  x[0] = 4;   y[0] = 1;
  x[1] = -2;  y[1] = 0;
  x[2] = 1;   y[2] = 5;
  
  cout << "        x = " << x << endl;
  cout << "        y = " << y << endl;
  
  // x *= -1
  x.scale (-1);
  
  cout << "now:    x = " << x << endl;
  
  add (x, y, z);
  
  cout << "z = x + y = " << z << endl;
}