Begin Exercise 2.29

chapter2.lisp

@@ -161,3 +161,22 @@ and upper bound."
   (if (null l)
       ()
       (append (deep-reverse (cdr l)) (list (car l)))))
+
+;; Exercise 2.29
+(defun make-mobile (left right)
+  (list left right))
+
+(defun left-branch (mobile)
+  (car mobile))
+
+(defun right-branch (mobile)
+  (cdr mobile))
+
+(defun make-branch (length structure)
+  (list length structure))
+
+(defun branch-length (branch)
+  (car branch))
+
+(defun branch-structure (branch)
+  (cdr branch))