Linked List and Pointers in the if statements

Hi I am studying basic Linked List right now. I am reading a related book and got stuck in this line.

 head = newNode;

"head" is pointer that was declared as a private member variable of another class called "NumberList" and will be initialized to nullptr by its constructor.
My question is what does pointer variable with "!" operator mean ?
In the book, it says "Because 'head' is a null pointer, the condition '!head' is true." How does this if statement work?
Last edited on
nullptr is basically an alias for 0, except it's "pointer-like". So
if (head == nullptr)
is equivalent to
if (head == 0)
In fact, 0 was the preferred value to use for null pointers before nullptr came around.

Now, checking equality to zero is the same as comparing to false, so
if (head == 0)
is equivalent to
if (head == false)

Finally, logically x == false is the same predicate as !x. (!x) == (x == false), no matter the value of x. So
if (head == false)
is equivalent to
if (!head)
@helios ,Thank you so much for great logical explanation !
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