CLISP Version: 2.49
Leaf Node
(value (NIL) (NIL))
Non-Leaf Node
(value (value (NIL) (NIL)) (NIL))
Code ("format" for debug only)
; (nil) means NULL
(defun binary-insert (root obj <)
(if (null (cdr root))
(progn
(format t "In Null [~A] => " root)
(setf (car root) obj)
(format t "mid [~A] => " root)
(setf (cdr root) '((nil) (nil)))
(format t "[~A]~%" root))
(if (funcall < obj (car root))
(progn
(format t "In Left [~A] => " root)
(binary-insert (nth 1 root) obj <)
(format t "[~A]~%" root)) ; Left
(progn
(format t "In Right [~A] => " root)
(binary-insert (nth 2 root) obj <)
(format t "[~A]~%" root)) ; Right
)
)
)
Test
[1]> (load "binary_tree.lisp")
;; Loading file binary_tree.lisp ...
;; Loaded file binary_tree.lisp
T
[2]> (setf *glb-rt* '(NIL))
(NIL)
[3]> (binary-insert *glb-rt* 10 #'<)
In Null [(NIL)] => mid [(10)] => [(10 (NIL) (NIL))]
NIL
[4]> *glb-rt*
(10 (NIL) (NIL))
[5]> (binary-insert *glb-rt* 5 #'<)
In Left [(10 (NIL) (NIL))] => In Null [(NIL)] => mid [(5)] => [
*** - Lisp stack overflow. RESET
It seems the program died after executing
(setf (cdr root) '((NIL) (NIL)))
Thanks....
[Update]
Before (setf (cdr root) '((NIL) (NIL))), the "root" is (5)
Another test
[6]> (setf glb-ls '(5))
(5)
[7]> (setf (cdr glb-ls) '((NIL) (NIL)))
((NIL) (NIL))
[8]> glb-ls
(5 (NIL) (NIL))
