в 14:21, 25 мая 2010

2010-05-25T14:21:06Z

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2010-05-25T10:28:27Z

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==Define operator []==

<source lang="cpp">
#include <iostream>
using namespace std;
class MyClass {
int a[3];
public:
MyClass(int i, int j, int k) {
a[0] = i;
a[1] = j;
a[2] = k;
}
int operator[](int i) {
return a[i];
}
};
int main()
{
MyClass object(1, 2, 3);
cout << object[1];
return 0;
}

</source>

==Index operator for class==

<source lang="cpp">
#include <iostream>
#include <stdlib.h>
using namespace std;
class sometype {
int a[3];
public:
sometype(int i, int j, int k)
{
a[0] = i;
a[1] = j;
a[2] = k;
}
int &operator[](int i);
};
int &sometype::operator[](int i)
{
if (i<0 || i>2)
{
cout << "Boundary error.\n";
exit(1);
}
return a[i];
}

int main(void)
{
sometype ob(1, 2, 3);
cout << ob[1];
cout << endl;
ob[1] = 25;
cout << endl;
cout << ob[1];
ob[3] = 44;
}

</source>

==Operator overload: new, delete, new[] and delete[]==

<source lang="cpp">
#include <iostream>
#include <cstdlib>
#include <new>
using namespace std;
class MyClass {
int x, y;
public:
MyClass() {
x = y = 0;
}

MyClass(int lg, int lt) {
x = lg;
y = lt;
}
void show() {
cout << x << " ";
cout << y << endl;
}
void *operator new(size_t size);
void operator delete(void *p);
void *operator new[](size_t size);
void operator delete[](void *p);
};
// overloaded new operator
void *MyClass::operator new(size_t size)
{
void *p;
cout << "In overloaded new.\n";

p = malloc(size);

if(!p) {

bad_alloc ba;

throw ba;
}
return p;
}
// delete operator overloaded
void MyClass::operator delete(void *p)
{

cout << "In overloaded delete.\n";

free(p);
}
// new operator overloaded for arrays.
void *MyClass::operator new[](size_t size)
{
void *p;
cout << "Using overload new[].\n";

p = malloc(size);

if( !p ) {

bad_alloc ba;

throw ba;
}

return p;
}
// delete operator overloaded for arrays.
void MyClass::operator delete[](void *p)
{
cout << "Freeing array using overloaded delete[]\n";

free(p);
}
int main()
{
MyClass *objectPointer1, *objectPointer2;
int i;
try {

objectPointer1 = new MyClass (10, 20);

} catch (bad_alloc xa) {

cout << "Allocation error for objectPointer1.\n";

return 1;;
}
try {

objectPointer2 = new MyClass [10]; // allocate an array

} catch (bad_alloc xa) {

cout << "Allocation error for objectPointer2.\n";

return 1;;
}
objectPointer1->show();

for( i = 0; i < 10; i++)
objectPointer2[i].show();
delete objectPointer1; // free an object
delete [] objectPointer2; // free an array
return 0;
}

</source>

==Overload [].==

<source lang="cpp">
#include <iostream>
using namespace std;
const int SIZE = 3;
class MyClass {
int a[SIZE];
public:
MyClass() {
register int i;
for(i = 0; i <SIZE; i++)
a[i] = i;
}
int operator[](int i) {
return a[i];

}
};
int main()
{
MyClass myObject;
cout << myObject[2];
return 0;
}

</source>

==Return a reference from [].==

<source lang="cpp">
#include <iostream>
using namespace std;
const int SIZE = 3;
class MyClass {
int a[SIZE];
public:
MyClass() {
register int i;
for(i = 0; i <SIZE; i++)
a[i] = i;
}
int &operator[](int i) {
return a[i];
}
};
int main()
{
MyClass myObject;
cout << myObject[2];
cout << " ";
myObject[2] = 25; // [] on left of =
cout << myObject[2]; // now displays 25
return 0;
}

</source>

==String class: Index characters and "=" operator==

<source lang="cpp">
#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;
class StringClass {
char *p;
int len;
public:
StringClass(char *s);
~StringClass() {
cout << "Freeing " << (unsigned) p << "\n";
delete [] p;
}
char *get() { return p; }
StringClass &operator=(StringClass &ob);
char &operator[](int i);
};
StringClass::StringClass(char *s)
{
int l;
l = strlen(s)+1;
p = new char [l];
if(!p) {
cout << "Allocation error\n";
exit(1);
}
len = l;
strcpy(p, s);
}
// = operator
StringClass &StringClass::operator=(StringClass &ob)
{
// see if more memory is needed
if(len < ob.len) { // need to allocate more memory
delete [] p;
p = new char [ob.len];
if(!p) {
cout << "Allocation error\n";
exit(1);
}
}
len = ob.len;
strcpy(p, ob.p);
return *this;
}
//
char &StringClass::operator[](int i)
{
if(i <0 || i>len-1) {
cout << "\nIndex value of ";
cout << i << " is out-of-bounds.\n";
exit(1);
}
return p[ i ];
}
int main()
{
StringClass a("Hello"), b("There");
cout << a.get() << "\n";
cout << b.get() << "\n";
a = b; // now p is not overwritten
cout << a.get() << "\n";
cout << b.get() << "\n";
cout << a[0] << a[1] << a[2] << endl;
a[0] = "X";
a[1] = "Y";
a[2] = "Z";
cout << a.get() << endl;
return 0;
}

</source>

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