Αντικειμενοστραφής Προγραμματισμός

Σε αυτή την ενότητα, θα δούμε παραδείγματα υπερφόρτωσης, τα οποία μεταβάλλουν τον αριστερό τελεστέο και μπορούν να υλοποιηθού μόνο ως μέλη της κλάσης.

Vector.hpp

#include <iostream>
#include <string>
#include <cstdlib>
using namespace std;
 
#ifndef _VECTOR_HPP_
#define _VECTOR_HPP_
 
class Vector {
  int *array;
  int size;
 
public:
  Vector(int length=0);
  Vector(const Vector& v);
  Vector(const Vector *v);
  ~Vector();
  int length() const;           // return Vector's length.
  int &valueAt(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 */
  Vector operator+(const Vector& v) const;
  Vector operator-(const Vector& v) const;
  Vector operator*(Vector& v) const;
 
  /* binary operators that modify left operand */
  Vector& operator=(const Vector& v);
  Vector& operator+=(const Vector& v);
  Vector& operator+=(int a);
  Vector& operator-=(const Vector& v);
  Vector& operator-=(int a);
  Vector& operator*=(const Vector& v);
  Vector& operator*=(int a);
  Vector& operator/=(int a);
  Vector& operator%=(int a);
  Vector& operator<<=(int a);
  Vector& operator>>=(int a);
  int &operator[](int a) const;
 
};
 
#endif

Vector.cpp

#include "Vector.hpp"
 
Vector::Vector(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;
}
 
int Vector::length() const { 
  return size; 
}
 
int &Vector::valueAt(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 << ", ";
  }
}
 
Vector& 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);
  return *this;
}
 
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;
}
 
Vector& Vector::operator+=(const Vector& v) {
  if(v.length() > size) {
    Vector n(v);
    n = n + *this;
    *this = n;
  }
  else {
    *this = *this + v;
  }
  return *this;
}
 
Vector& Vector::operator+=(int a) {
  for(int i=0; i<size; i++)
    array[i] += a;
  return *this;
}
 
Vector& Vector::operator-=(const Vector& v) {
  if(v.length() > size) {
    Vector n(v);
    n = n - *this;
    *this = n;
  }
  else {
    *this = *this - v;
  }
  return *this;
}
 
Vector& Vector::operator-=(int a) {
  for(int i=0; i<size; i++)
    array[i] -= a;
  return *this;
}
 
Vector& Vector::operator*=(const Vector& v) {
  if( v.size != size )
    return *this;
 
  for(int i=0; i<size; i++)
    array[i] *= v.array[i];  
  return *this;
}
 
Vector& Vector::operator*=(int a) {
  for(int i=0; i<size; i++)
    array[i] *= a;
  return *this;
}
 
Vector& Vector::operator/=(int a) {
  for(int i=0; i<size; i++)
    array[i] /= a;
  return *this;
}
 
Vector& Vector::operator%=(int a) {
  for(int i=0; i<size; i++)
    array[i] %= a;
  return *this;
}
 
Vector& Vector::operator<<=(int a) {
  for(int i=0; i<size; i++)
    array[i] <<= a;
  return *this;
}
 
Vector& Vector::operator>>=(int a) {
  for(int i=0; i<size; i++)
    array[i] >>= a;
  return *this;
}
 
int &Vector::operator[](int pos) const {
  return array[pos];
}

VectorUsage.cpp

#include "Vector.hpp"
 
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 , g;
  f = g = v;
  f.print(msg="Vector f:  ");
  g.print(msg="Vector g:  ");
 
  g = f += v;
  g.print(msg="g = 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:  ");
 
  cout << "v[2]:  " << v[2] << endl;
  v[2] = 100;
  v.print(msg="[v[2] = 100] v:  ");  
}