C++: Can't work with simple pointers?

I apologize as this is so simple, I was working with my own XOR swap method and wanted for the he开发者_如何转开发ck of it compare the speed difference between reference and pointer use (do not spoil it for me!)

My XOR ptr function is as follows:

 void xorSwapPtr (int *x, int *y) {
     if (x != y && x && y) {
         *x ^= *y;
         *y ^= *x;
         *x ^= *y;
     }
 }

I copied this to a xorSwapRef function which just uses refs (int &x, etc.) anywho:

I use it like this but I get the error error: invalid conversion from ‘int’ to ‘int*’

int i,x,y = 0;
for(i=0;i<=200000;i++) {
    x = rand();
    y = rand(); 
    xorSwapPtr(x, y); //error here of course
}

How would I use the pointer function with ints, like the ref one? I just wonder because the example xor function I found in a book uses pointers, hence my wanting to test.

x and y are ints; xorSwapPtr takes two int*s, so you need to pass the addresses of x and y, not x and y themselves:

xorSwapPtr(&x, &y);

The syntax can be confusing... When you want to pass a pointer to something, you usually take the address of it, like &something. However, when declaring a function signature, and you want to define one of the parameters to be a reference to a Type called somethingElse, then you would use Type &somethingElse. Both of these use the & token, but they mean 2 different things (different semantics for the token &, just like * could mean multiply, define a pointer to, or dereference a pointer, each depending upon its grammatical place in the code).

void foo(int *x, int *y); // declare a function that takes two pointers to int
void bar(int &x, int &y); // declare a function that takes two references to int

now let's use them...

int i, j;
foo(&i, &j);  // pass in the address of i and the address of j
bar(i, j);  // pass in a reference to i and a reference to j
// can't tell by the call that it is a reference - could be "by value"
// so you gotta look at the function signature

This bit

xorSwapPtr(x, y);

Needs to be

xorSwapPtr(&x, &y);

Hope this helps