CODEWITHSUNDEEP
c++
KucheKajiMyau
KucheKajiMyau

Reputation: 39

What does *& do in c++

In one of my lectures we had this function that adds elements to a non stl binary three. What does the *& do exactly? I know that & gets the address of a variable and that * allows us to access the value at a particular address. Do they have a different meaning when together? Also if I was to call this function in main, what do I do with the t pointer? 

void add(int n, elem *&t)
 {  
    if (t==NULL)  //ако е достигнат празен указател или дървото е празно  
    {   
        t=new elem;
        t->key=n;  
        t->left=t->right=NULL;      //left и right са NULL, тъй като новият елемент няма наследници  
    }  else      //ако достигнатото място е заето от друг елемент  
    {   
        if (t->key<n) //ако новодобавения елемент е по-голям от текущия, то указателя се измества надясно,извиква се рекурсивно add с указателя вдясно     
            add(n,t->right);   
        else    
        {
            if (t->key>n) //с цел да се елиминират повтарящи се елементи се прави втората проверка      
                add(n,t->left); // извиква се рекурсивно add с указателя вляво 
        }  
    } 
}

Here is the structure as well:

struct elem 
{ 
    char key; 
    elem *left;  //lqv naslednik
    elem *right; // desen naslednik
}*root=NULL;  // v sluchai che nqma koren

Upvotes: 0

Views: 874

Answers (1)

Ron
Ron

Reputation: 15511

In your case, it is a part of the elem*& function parameter reference type. Used to pass an object of type elem* by reference. Pointers are just like any other variables/objects. Passing them by reference allows us to change the pointer value in a function.

The elem* &t in your void add(int n, elem *&t) signature does not "get the address of a variable". It means the type of the function parameter is a reference type. It just so happens it is a pointer reference type in your case.

Do not confuse the address-of operator, which is & with a reference type signature of T& param_name. In your case, the T is elem*.

It could also mean: dereference the address of an object if used in the following context:

#include <iostream>

int main()
{
    int x = 123;
    std::cout << *&x;
}

Upvotes: 4

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