References and de-references

[account1]

http://www.cplusplus.com/doc/tutorial/classes2/

What does it mean to have a -> de-reference sign in a if statement and why is the & reference needed in the parameter for 'isitme' function?

#include <iostream>
using namespace std;

class CDummy {
  public:
    int isitme (CDummy& param);
};

int CDummy::isitme (CDummy& param)
{
  if (&param == this) return true;
  else return false;
}

int main () {
  CDummy a;
  CDummy* b = &a;
  if ( b->isitme(a) )
    cout << "yes, &a is b";
  return 0;
}

[Danny Toledo]

Check out the section on data structures, it explains the arrow operator (under "Pointers to structures):

http://www.cplusplus.com/doc/tutorial/structures/

The fact that it is in an if statement is irrelevant.

From the above link, we can see that b->isitme(a) is equivalent to (*b).isitme(a)

why is the & reference needed in the parameter for 'isitme' function

There is an explanation of this (pass-by-reference that is) too:

http://www.cplusplus.com/doc/tutorial/functions2/

In your example, param is just a reference to the argument passed to it.

Maybe an example of references will make a little more sense:

int a = 10;
int b = a; //b is a copy of a
int a_ref = a;//a_ref is a reference to a 

Play with the above code snippet a little. Print the values. Print the address of the variables. An example run (the address of a at the end is just to make comparing it to that of a_ref easier):

    a: 10
    b: 10
a_ref: 10

    address of a: 0x28ff08
    address of b: 0x28ff0c
address of a_ref: 0x28ff08
 addr again of a: 0x28ff08

As we can see b is a copy of a and a_ref is a, just a different name. Thus, when we use a reference variable as a parameter for a function, the parameter is just an alias for the argument. That means that the argument passed is directly accessible within that function (under the name of the reference of course).