в 14:21, 25 мая 2010

2010-05-25T14:21:06Z

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2010-05-25T10:28:23Z

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==Demo: Overload the +, -, and = relative to MyClass.==

<source lang="cpp">
#include <iostream>
using namespace std;
class MyClass {
int x, y;
public:
MyClass() {
x=0;
y=0;
}
MyClass(int i, int j) {
x=i;
y=j;
}
void getXY(int &i, int &j) {
i=x;
j=y;
}
MyClass operator+(MyClass object2);
MyClass operator-(MyClass object2);
MyClass operator=(MyClass object2);
};
MyClass MyClass::operator+(MyClass object2){
MyClass temp;
temp.x = x + object2.x;
temp.y = y + object2.y;
return temp;
}
MyClass MyClass::operator-(MyClass object2){
MyClass temp;
temp.x = x - object2.x;
temp.y = y - object2.y;
return temp;
}
MyClass MyClass::operator=(MyClass object2)
{
x = object2.x;
y = object2.y;
return *this; // return the object that is assigned
}
int main()
{
MyClass object1(10, 10), object2(5, 3), object3;
int x, y;
object3 = object1 + object2; // add two objects - this calls operator+()
object3.getXY(x, y);
cout << "(object1+object2) X: " << x << ", Y: " << y << endl;
object3 = object1 - object2; // subtract two objects
object3.getXY(x, y);
cout << "(object1-object2) X: " << x << ", Y: " << y << endl;
object3 = object1; // assign an object
object3.getXY(x, y);
cout << "(object3=object1) X: " << x << ", Y: " << y << endl;
return 0;
}

</source>

==Overload - (subtraction) so that it removes the first occurrence of the substring on the right from the string on the left and returns the result.==

<source lang="cpp">
#include <iostream>
#include <string>
using namespace std;
string operator-(const string &left, const string &right);
string operator-=(string &left, const string &right);
int main()
{
string str("This is a test.");
string res_str;
cout << "Contents of str: " << str << "\n\n";
res_str = str - "is";
cout << res_str << "\n\n";
res_str -= "is";
cout << res_str << "\n\n";
cout << str;
return 0;
}

string operator-(const string &left, const string &right) {
string::size_type i;
string result(left);
i = result.find(right);
if(i != string::npos)
result.erase(i, right.size());
return result;
}

string operator-=(string &left, const string &right) {
string::size_type i;
i = left.find(right);
if(i != string::npos)
left.erase(i, right.size());
return left;
}

</source>

==overload the - operator==

<source lang="cpp">
#include <iostream>
#include <iomanip>
#include <string.h>
using namespace std;
class String {
public:
char *operator +(char *append_str)
{ return(strcat(buffer, append_str)); };

char *operator -(char letter);
String(char *string)
{ strcpy(buffer, string);
length = strlen(buffer); }
void show_string(void) { cout << buffer; };
private:
char buffer[256];
int length;
};
char *String::operator -(char letter)
{
char target[256];
int i, j;
for (i = 0, j = 0; buffer[j]; j++)
if (buffer[j] != letter)
target[i++] = buffer[j];
target[i] = NULL;

for (i = 0, j = 0; (buffer[j] = target[i]); i++, j++)
;
return(buffer);
}
int main(void)
{
String title("C");
title = title + "B\n";
title.show_string();
title = title - "0";
title.show_string();
}

</source>

==Overload the - relative to MyClass class 1. ==

<source lang="cpp">
#include <iostream>
using namespace std;
class MyClass {
int x, y;
public:
MyClass() {
x=0;
y=0;
}
MyClass(int i, int j) {
x=i;
y=j;
}
void getXY(int &i, int &j) {
i=x;
j=y;
}
MyClass operator-(MyClass object2); // binary minus
MyClass operator-(); // unary minus
};
MyClass MyClass::operator-(MyClass object2)
{
MyClass temp;
temp.x = x - object2.x;
temp.y = y - object2.y;
return temp;
}
// Overload unary - for MyClass class.
MyClass MyClass::operator-()
{
x = -x;
y = -y;
return *this;
}
int main()
{
MyClass object1(10, 10), object2(5, 7);
int x, y;
object1 = object1 - object2; // subtraction
object1.getXY(x, y);
cout << "(object1-object2) X: " << x << ", Y: " << y << endl;
object1 = -object1; // negation
object1.getXY(x, y);
cout << "(-object1) X: " << x << ", Y: " << y << endl;
return 0;
}

</source>

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