C++ function parameter takes an address of a pointer as an argument. How is this used? What is it for?

Question

Imagine a function like this:

 function(Human *&human){
      // Implementation
 }

Can you explain what exactly a *& is? And what would it be used for? How is different than just passing a pointer or a reference? Can you give a small and explanatory sample?

Thank you.

Answer 1

It is like a double pointer. You're passing the pointer by reference allowing the 'function' function to modify the value of the pointer.

For example 'human' could be pointing to Jeff and function could modify it to point to Ann.

Human ann("Ann");

void function(Human *& human)
{
    human = &ann;
}

int main()
{
    Human jeff("Jeff");
    Human* p = &jeff;
    function(p);  // p now points to ann
    return 0;
}