Question

Possible Duplicate:
Difference between pointer to a reference and reference to a pointer

I am newbie in C++ and I work on a pretty complicated project. When I tried to figure out something, I saw one interesting thing:

n->insertmeSort((Node *&)first);

When we deep into insertmeSort, we can see the same:

    void Node::insertme(Node *&to)
{
   if(!to) {
      to=this;
      return;
   }
   insertme(value>to->value ? to->right : to->left);
}

So the reason of my question is: Node *& – asterisk and ampersand, for what?

It looks pretty tricky, and interesting to me.

Answer 1

It a reference to a pointer. Like any regular reference, but the underlying type is a pointer.

Prior to references pointer-by-reference had to be done with double-pointers (and some C-minded folk still do, I occasionally being one of them).

Lest there be any doubt, try this to really sink it in:

#include <iostream>
#include <cstdlib>

void foo (int *& p)
{
    std::cout << "&p: " << &p << std::endl;
}

int main(int argc, char *argv[])
{
    int *q = NULL;
    std::cout << "&q: " << &q << std::endl;
    foo(q);

    return EXIT_SUCCESS;
}

Output (your values will be different , but &p == &q)

&q: 0x7fff5fbff878
&p: 0x7fff5fbff878

It is hopefully pretty clear that p in foo() is indeed a reference to pointer q in main().