"Pat Monardo" <[EMAIL PROTECTED]> writes:
> I dont understand. For example this is typical from red-black tree
> (if (eq (p z) (left (p (p z))))
>
> (let ((y (right (p (p z)))))
>
> (cond ((eq (color y) :RED)
>
> (setf (color (p z)) :BLACK)
>
> (setf (color y) :BLACK)
>
> (setf (color (p (p z))) :RED)
>
> (setf z (p (p z))))
>
> etc..
>
> (sorry the formatting is strange on move to windows from linux emacs; dont
> really know emacs but I am using ILISP)
>
> where p is CLRS speak for parent. how would you improve something
> like this?
What about something like
(let ((parent (parent node))
(grandparent (parent parent)))
(if (eq parent (left grandparent))
(let ((neighbor (right grandparent)))
(cond ((eq (color neighbor) :RED)
(setf (color parent) :BLACK)
(setf (color neighbor) :BLACK)
(setf (color grandparent)) :RED)
(setf node grandparent))
)))
Nicolas.
