Project 1999 - itsy bitsy bug

Code:

if (NULL == vertex->right() == vertex->left())

      // wutdo

Seems legit, if both values equal NULL, we wutdo.

THAT IS UNTIL we take apart and realize how the compiler sees this statement differently from us. NULL is #define'd as 0. Boolean values are represented by 1 = true, 0 = false

So if the right vertex was NULL, it would evaluate that part of the equation to True before moving on. Now we would basically have the following:

Code:

if (1 == vertex->left())

Not what we want at all.

Likewise, if vertex->right() was not NULL, it would evaluate to false. So now we have:

Code:

if (0 == vertex->left()

This is also wrong, since right had a value.

Correct:

Code:

if (vertex->right() == NULL && vertext->left() == NULL)

http://www.pc-xp.com/wp-content/uplo...bug_no_400.png