Why cannot I directly use returned pointer as parameter in function call of insert?

Question

Here's the prototype of the function:

void BinaryDimonTree::insert(int x, int y, int level, TreeNode *&cur)

in the function, I tried to call:

insert(x, y, ++level, cur->getLeftChild());

and here's getLeftChild:

TreeNode* TreeNode::getLeftChild() const {
    return this->left;
}

Then, it reports an error:

no instance of overloaded function "BinaryDimonTree::insert" matches the argument list -- argument types are: (int, int, int, TreeNode *)

If I change my code this way:

TreeNode *child = cur->getLeftChild();
insert(x, y, ++level, child);

No error would be reported.

I wonder why this problem occurs and how to solve it if I want to directly use the function return value as the parameter?

Thanks a lot!

You can't use an implicit temp as a reference argument. How would you refer to it after the call? — 500 - Internal Server Error, Apr 15 '19 at 12:27

Dmitry Gordon · Accepted Answer · 2019-04-16T09:17:33.023

2

The last argument of your insert function is non-const reference to a pointer. In the call:

insert(x, y, ++level, cur->getLeftChild());

the last argument is a temporary value of TreeNode * type, that cannot bind to the TreeNode * &. You can find a good explanation here

edited Apr 16 '19 at 09:17

answered Apr 15 '19 at 12:30

Dmitry Gordon

1 Answers1