[funds-cvs] r30 - trunk/funds/src/trees

[abaine at common-lisp.net]

Author: abaine
Date: Wed Jun 20 13:06:54 2007
New Revision: 30

Modified:
   trunk/funds/src/trees/avl-tree.lisp
Log:
Minor semantic changes.

Modified: trunk/funds/src/trees/avl-tree.lisp
==============================================================================
--- trunk/funds/src/trees/avl-tree.lisp	(original)
+++ trunk/funds/src/trees/avl-tree.lisp	Wed Jun 20 13:06:54 2007
@@ -103,6 +103,11 @@
 in their absolute values, by more than one."
   (> (abs (height-difference left right)) 1))
 
+(defun balanced (left right)
+  "Whether the heights of the given sub-trees differ,
+in their absolute values, by no more than one."
+  (< -2 (height-difference left right) 2))
+
 (defun height-difference (a b)
   "The difference in heights of the given sub-trees."
   (- (avl-height a) (avl-height b)))
@@ -116,12 +121,12 @@
 (defun left-heavy (tree)
   "Whether the given imbalanced AVL Tree has a left sub-tree
 taller than its right sub-tree."
-  (< (balance-factor tree) 0))
+  (minusp (balance-factor tree)))
 
 (defun right-heavy (tree)
   "Whether the given imbalanced AVL Tre has a right sub-tree
 taller than its left sub-tree."
-  (> (balance-factor tree) 0))
+  (plusp (balance-factor tree)))
 
 (defun balance-factor (tree)
   "The difference in heights of the right sub-tree and left