Diff Reference b/w Pointer

[Radde]

HI all,
What are the major diff betweeb refernce and pointer in C++..

Cheers...

[Victor Bazarov]

Radde wrote:
> What are the major diff betweeb refernce and pointer in C++..

What does your favourite C++ book say about them, and what don't
you understand there? Have you tried reading the FAQ on this
topic?

[upashu2]

1.pointers can be null, references not
2. pointers can be dangling, references not.
3. pointers can be changed to point to other object, references not.
4. while passing parameters through pointers, copies of pointers are
made , 4 byte for each pointer on 32bit system, and while passing
parameters through refrences, compiler can optimize further and even
can save the 4 byte copy operation.
5. In previous case, while using pointer , you have to use & operator,
and using references, you save one key typing time.
6. When u will combine pointer and references, u can have a situtation
like this
int *p = new int;
int & q =*p;
......
int *r = &q;
delete r; ///somewhere in program
.........
q = 20; ///what is happening here?

[Gianni Mariani]

upashu2 wrote:
> 1.pointers can be null, references not
> 2. pointers can be dangling, references not.

Doesn't point 6 show how references can be "dangling" ?

> 3. pointers can be changed to point to other object, references not.
> 4. while passing parameters through pointers, copies of pointers are
> made , 4 byte for each pointer on 32bit system, and while passing
> parameters through refrences, compiler can optimize further and even
> can save the 4 byte copy operation.
> 5. In previous case, while using pointer , you have to use & operator,
> and using references, you save one key typing time.
> 6. When u will combine pointer and references, u can have a situtation
> like this
> int *p = new int;
> int & q =*p;
> ......
> int *r = &q;
> delete r; ///somewhere in program
> .........
> q = 20; ///what is happening here?
>

7. It is an error not to initialize a reference to a valid object.
8. References can increase the lifetime of a temporary to the lifetime
of the reference, pointers can not (see below).

#include <iostream>
#include <ostream>

struct A
{
A()
{
std::cout << "A default\n";
}

A( const A & )
{
std::cout << "A copy\n";
}

A & operator= ( const A & )
{
std::cout << "A operator =\n";
return * this;
}

~A()
{
std::cout << "A Destruct\n";
}
};

int main()
{
{
const A & a = A();

std::cout << "Temporary lives !\n";

A y( a );
}

std::cout << "Temporary is gone !\n";

{
const A * a = & A();

std::cout << "Temporary is gone already - a dangles!\n";
}
}