mutual_recursion.clj

sicp.chapter1.2-2> (defn my-odd? [n]
                     (letfn [(odd? [n]
                               (if (zero? n)
                                 false
                                 (even? (dec n))))
                             (even? [n]
                               (if (zero? n)
                                 true
                                 (odd? (dec n))))]
                       (odd? n)))
#'sicp.chapter1.2-2/my-odd?
sicp.chapter1.2-2> (map my-odd? (range (inc 5)))
(false true false true false true)
sicp.chapter1.2-2> (my-odd? 100)
false
sicp.chapter1.2-2> (my-odd? 1000)
false
sicp.chapter1.2-2> (my-odd? 10000)
StackOverflowError   clojure.lang.Numbers$LongOps.dec (Numbers.java:562)
sicp.chapter1.2-2> (defn my-odd? [n]
                     (letfn [(odd? [n]
                               (if (zero? n)
                                 false
                                 #(even? (dec n))))
                             (even? [n]
                               (if (zero? n)
                                 true
                                 #(odd? (dec n))))]
                       (trampoline odd? n)))
#'sicp.chapter1.2-2/my-odd?
sicp.chapter1.2-2> (my-odd? 10000)
false
sicp.chapter1.2-2> (my-odd? 100000)
false

mutual_recursion.lisp

CL-USER> (defun my-oddp (n)
           (labels ((odd? (n)
                      (if (zerop n)
                          nil
                          (even? (1- n))))
                    (even? (n)
                      (if (zerop n)
                          t
                          (odd? (1- n)))))
             (odd? n)))
MY-ODDP
CL-USER> (mapcar #'my-oddp '(0 1 2 3 4 5))
(NIL T NIL T NIL T)
CL-USER> (my-oddp 100000)
NIL