What does this use of the '&&' operator mean in C++?

Question

I am working on a project to implement a Binary Search Tree, root is a pointer to a Node struct, and I ran into a piece of code online with the following line:

if ((root->left) && (root->right))

is the code above equivalent to:

if (root->left == root->right)

if not can someone please explain the difference to me? I thought you needed to have some sort of comparative operator (==, !=).

Answer 1

You did not post the code (and in C++ lot of things depend on context) but I believe that:

if ((root->left) && (root->right))

Is equivalent to:

if ((root->left != nullptr) && (root->right != nullptr))

The pointers in C++ can be implicitly converted to bool that is true when the pointer is a non-null pointer. The && operator means 'and'. So for the if condition to be true , both root->left and root->right are non-null pointers.

The relevant part from standard [conv.bool]

A prvalue of arithmetic, unscoped enumeration, pointer, or pointer to member type can be converted to a prvalue of type bool. A zero value, null pointer value, or null member pointer value is converted to false; any other value is converted to true. For direct-initialization , a prvalue of type std::nullptr_t can be converted to a prvalue of type bool; the resulting value is false.