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2010-05-25T14:21:17Z

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2010-05-25T10:30:35Z

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==Define -, + and = for the ThreeD class==

<source lang="cpp">#include <iostream>
using namespace std;

class ThreeD {
int x, y, z;
public:
ThreeD() { x = y = z = 0; }
ThreeD(int i, int j, int k) { x = i; y = j; z = k; }

ThreeD operator+(ThreeD op2); // op1 is implied
ThreeD operator=(ThreeD op2); // op1 is implied
ThreeD operator-(ThreeD op2); // op1 is implied
void show() ;
};
// Overload subtraction.
ThreeD ThreeD::operator-(ThreeD op2)
{
ThreeD temp;

temp.x = x - op2.x;
temp.y = y - op2.y;
temp.z = z - op2.z;
return temp;
}

// Overload +.
ThreeD ThreeD::operator+(ThreeD op2)
{
ThreeD temp;

temp.x = x + op2.x;
temp.y = y + op2.x;
temp.z = z + op2.z;
return temp;
}

// Overload assignment.
ThreeD ThreeD::operator=(ThreeD op2)
{
x = op2.x;
y = op2.y;
z = op2.z;
return *this;
}

// Show X, Y, Z coordinates.
void ThreeD::show()
{
cout << x << ", ";
cout << y << ", ";
cout << z << "\n";
}

int main()
{
ThreeD a(1, 2, 3), b(10, 10, 10), c;

cout << "Original value of a: ";
a.show();
cout << "Original value of b: ";
b.show();

c = a - c;
cout << "a - c: ";
c.show();

cout << "\n";

return 0;
}</source>
<pre class=codeResult>Original value of a: 1, 2, 3
Original value of b: 10, 10, 10
a - c: 1, 2, 3</pre>

==Overload assignment for Point==

<source lang="cpp">#include <iostream>
using namespace std;
class Point {
int x, y;
public:
Point() {} // needed to construct temporaries
Point(int px, int py) {
x = px;
y = py;
}
void show() {
cout << x << " ";
cout << y << "\n";
}
Point operator+(Point op2);
Point operator-(Point op2);
Point operator=(Point op2);
Point operator++();
};
// Overload + for Point.
Point Point::operator+(Point op2)
{
Point temp;
temp.x = op2.x + x;
temp.y = op2.y + y;
return temp;
}
// Overload - for Point.
Point Point::operator-(Point op2)
{
Point temp;
// notice order of operands
temp.x = x - op2.x;
temp.y = y - op2.y;
return temp;
}
// Overload asignment for Point.
Point Point::operator=(Point op2)
{
x = op2.x;
y = op2.y;
return *this; // i.e., return object that generated call
}
// Overload prefix ++ for Point.
Point Point::operator++()
{
x++;
y++;
return *this;
}
int main()
{
Point ob1(10, 20), ob2( 5, 30), ob3(90, 90);
ob1.show();
ob2.show();
++ob1;
ob1.show(); // displays 11 21
ob2 = ++ob1;
ob1.show(); // displays 12 22
ob2.show(); // displays 12 22
ob1 = ob2 = ob3; // multiple assignment
ob1.show(); // displays 90 90
ob2.show(); // displays 90 90
return 0;
}</source>
<pre class=codeResult>10 20
5 30
11 21
12 22
12 22
90 90
90 90</pre>

==Overloading the copy assignment operator==

<source lang="cpp">#include <iostream>
#include <cstring>
using std::cout;
using std::endl;
using namespace std;
class MyString {
public:
MyString(const char* pText) {
pString = new char[ strlen(pText) + 1 ];
std::strcpy(pString, pText);
}
~MyString() {
cout << endl << "Destructor called." << endl;
delete[] pString;
}
MyString& operator=(const MyString& String) {
cout << endl << "calling =." << endl;
if(this == &String)
return *this;
delete[] pString;
pString = new char[ strlen(String.pString) + 1];
// Copy right operand string to left operand
std::strcpy(this->pString, String.pString);
return *this;
}

char* getString() const{ return pString; }
private:
char* pString;
};
int main() {
MyString warning("There is a String");
MyString standard("");
cout << warning.getString();
cout << standard.getString();
standard = warning;
cout << warning.getString();
cout << standard.getString();
cout << endl;
return 0;
}</source>
<pre class=codeResult>There is a String
calling =.
There is a StringThere is a String
Destructor called.
Destructor called.</pre>

==Overload operator plus (=)==

<source lang="cpp">#include <iostream>

class MyType
{
public:
MyType();
int GetAge() const { return *itsAge; }
int GetWeight() const { return *itsWeight; }
void SetAge(int age) { *itsAge = age; }
MyType operator=(const MyType &);

private:
int *itsAge;
int *itsWeight;
};

MyType::MyType()
{
itsAge = new int;
itsWeight = new int;
*itsAge = 5;
*itsWeight = 9;
}

MyType MyType::operator=(const MyType & rhs)
{
if (this == &rhs)
return *this;
delete itsAge;
delete itsWeight;
itsAge = new int;
itsWeight = new int;
*itsAge = rhs.GetAge();
*itsWeight = rhs.GetWeight();
return *this;
}

int main()
{
MyType myObject;
std::cout << "myObject"s age: " << myObject.GetAge() << std::endl;
std::cout << "Setting myObject to 6...\n";
myObject.SetAge(6);
MyType whiskers;
std::cout << "whiskers" age: " << whiskers.GetAge() << std::endl;
std::cout << "copying myObject to whiskers...\n";
whiskers = myObject;
std::cout << "whiskers" age: " << whiskers.GetAge() << std::endl;
return 0;
}</source>
<pre class=codeResult>myObject"s age: 5
Setting myObject to 6...
whiskers" age: 5
copying myObject to whiskers...
whiskers" age: 6</pre>

==Use overloaded +===

<source lang="cpp">#include <iostream>
#include <string>
using namespace std;
int main()
{
string s1( "cat" ), s2, s3;
s2 = s1;
s3.assign( s1 );
cout << "s1: " << s1 << "\ns2: " << s2 << "\ns3: "
<< s3 << "\n\n";
// overloaded +=
s3 += "pet"; // create "carpet"
return 0;
}</source>

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