Αντικειμενοστραφής Προγραμματισμός

Παρακάτω θα δούμε την υπερφόρτωση τελεστών που μεταβάλλουν τον αριστερό τελεστέο. Οι τελεστές αυτής της κατηγορίας μπορούν να υλοποιηθούν μόνο από μέλη της κλάσης και όχι από φιλικές συναρτήσεις. Οι τελεστές περιγράφονται στον παρακάτω πίνακα.

Vector.cpp

#include <iostream>
#include <string>
#include <cstdlib>
using namespace std;
 
class Vector {
  int *array;
  unsigned int size;
 
public:
  Vector(unsigned int length=0);
  Vector(const Vector &v);
  Vector(const Vector *v);
  ~Vector();
  unsigned int length() const;           // return Vector's length.
  int &valueAt(unsigned int pos) const;  // return a reference to element at position pos
  int find(int a) const;      // check if a exists in Vector. Return it position >0 or -1 
                              // if not element not found
 
  void print() const;           // print vector values to standard output
  void print(string &msg) const;  // print vector values to standard output
 
  /* binary operators that don't modify left operand */
  void operator=(const Vector &v);
  Vector operator+(const Vector &v) const;
  Vector operator-(const Vector &v) const;
  Vector operator*(Vector &v) const;
 
  /* binary operators that modify left operand */
  void operator+=(const Vector &v);
  void operator+=(int a);
  void operator-=(const Vector &v);
  void operator-=(int a);
  void operator*=(const Vector &v);
  void operator*=(int a);
  void operator/=(int a);
  void operator%=(int a);
  void operator<<=(int a);
  void operator>>=(int a);
  int &operator[](int a) const;
 
};
 
Vector::Vector(unsigned int length) {
  size = length;
  array = new (nothrow) int[size];
  if(array==NULL) {
    cerr << "Memory allocation failure!" << endl;
    exit(-1);
  }
  for(int i=0; i<size; i++)
    array[i] = 0;
}
 
Vector::Vector(const Vector &v) {
  size = v.length();
  array = new (nothrow) int[size];
  if(array==NULL) {
    cerr << "Memory allocation failure!" << endl;
    exit(-1);
  }
  for(int i=0; i<size; i++)
    array[i] = v.valueAt(i);
}
 
Vector::Vector(const Vector *v) {
  size = v->length();
  array = new (nothrow) int[size];
  if(array==NULL) {
    cerr << "Memory allocation failure!" << endl;
    exit(-1);
  }
  for(int i=0; i<size; i++)
    array[i] = v->valueAt(i);
}
 
Vector::~Vector() {
  delete [] array;
}
 
unsigned int Vector::length() const { 
  return size; 
}
 
int &Vector::valueAt(unsigned int pos) const {
  if(pos>=length()) {
     cerr << "Invalid access position!\n";
     return array[size-1];
  }
  return array[pos];
}
 
int Vector::find(int a) const {
  for(int i=0; i<size; i++)
    if(array[i] == a)
      return i;
    return -1;
}
 
void Vector::print() const {
  for(int i=0; i<size; i++) {
    cout << array[i];
    if(i==size-1)
      cout << endl;
    else
      cout << ", ";
  }
}
 
void Vector::print(string &msg) const {
  cout << msg;
  for(int i=0; i<size; i++) {
    cout << array[i];
    if(i==size-1)
      cout << endl;
    else
      cout << ", ";
  }
}
 
void Vector::operator=(const Vector &v) {
  if(array!=NULL)
    delete [] array;
  size = v.length();
  array = new (nothrow) int[size];
  if(array==NULL) {
    cerr << "Memory allocation failure!" << endl;
    exit(-1);
  }
  for(int i=0; i<size; i++)
    array[i] = v.valueAt(i);  
}
 
Vector Vector::operator+(const Vector &v) const {
  int length;
  if (size > v.length())
    length = size;
  else
    length = v.length();
  Vector n(length);
  for(int i=0; i<length; i++) {
    int sum = 0;
    if(i<size)
      sum += array[i];
    if(i<v.length())
      sum += v.array[i];
    n.array[i] = sum;
  }
  return n;
}
 
Vector Vector::operator-(const Vector &v) const {
  int length;
  if (size > v.length())
    length = size;
  else
    length = v.length();
  Vector n(length);
  for(int i=0; i<length; i++) {
    int sum = 0;
    if(i<size)
      sum += array[i];
    if(i<v.length())
      sum -= v.array[i];
    n.array[i] = sum;
  }
  return n;
}
 
void Vector::operator+=(const Vector &v) {
  if(v.length() > size) {
    Vector n(v);
    n = n + *this;
    *this = n;
  }
  else {
    *this = *this + v;
  }
}
 
void Vector::operator+=(int a) {
  for(int i=0; i<size; i++)
    array[i] += a;
}
 
void Vector::operator-=(const Vector &v) {
  if(v.length() > size) {
    Vector n(v);
    n = n - *this;
    *this = n;
  }
  else {
    *this = *this - v;
  }
}
 
void Vector::operator-=(int a) {
  for(int i=0; i<size; i++)
    array[i] -= a;
}
 
void Vector::operator*=(const Vector &v) {
  if( v.size != size )
    return;
 
  for(int i=0; i<size; i++)
    array[i] *= v.array[i];  
}
 
void Vector::operator*=(int a) {
  for(int i=0; i<size; i++)
    array[i] *= a;
}
 
void Vector::operator/=(int a) {
  for(int i=0; i<size; i++)
    array[i] /= a;
}
 
void Vector::operator%=(int a) {
  for(int i=0; i<size; i++)
    array[i] %= a;
}
 
int &Vector::operator[](int pos) const {
  return array[pos];
}
 
void Vector::operator<<=(int a) {
  int *array_new = new (nothrow) int [size+1];
  if(array_new==NULL) {
    cerr << "Memory allocation failure in operator<< !" << endl;
    exit(-1);
  }
  for(int i=0; i<size; i++)
    array_new[i] = array[i];
  array_new[size] = a;
  size++;
  delete [] array;
  array = array_new;
}
 
void Vector::operator>>=(int a) {
  int pos = find(a);
  if(pos<0)
    return;  
  int *array_new = new (nothrow) int [size-1];
  if(array_new==NULL) {
    cerr << "Memory allocation failure in operator<< !" << endl;
    exit(-1);
  }
  for(int i=0; i<size; i++) {
    if(i<pos)
      array_new[i] = array[i];
    if(i==pos)
      continue;
    if(i>pos)
      array_new[i-1] = array[i];
  }  
  size--;
  delete [] array;
  array = array_new;
}
 
 
int main() {
  Vector v(5);
  v.valueAt(0) = 2;  v.valueAt(1) = 3;
  v.valueAt(2) = 4;  v.valueAt(3) = 5;  v.valueAt(4) = 6;
 
  string msg = "Vector v:  ";  
  v.print(msg);
 
  Vector f = v;
  v.print(msg="Vector f:  ");
 
  f += v;
  f.print(msg="f += v:  ");
  f -= v;
  f.print(msg="f -= v:  ");
  f *= v;
  f.print(msg="f *= v:  ");
 
  f = v;  
  f += 2;
  f.print(msg="f += 2:  ");
  f -= 2;
  f.print(msg="f -= 2:  ");
  f *= 2;
  f.print(msg="f *= 2:  ");
  f /= 2;
  f.print(msg="f /= 2:  ");
  f %= 2;
  f.print(msg="f %= 2:  ");
 
  f = v;
  int k = f[2];
  cout << "k :  " << k << endl;
  f[2] = 100;
  f.print(msg="f[2] = 100:  ");  
}