>>985
Little Lisper には演習問題があるのでひとつ紹介しよう。

演習9.4：

With the Y-combinator we can reduce the number of arguments on which a function has to recur.
For example, member can be rewritten as:

(define member-Y
(lambda (a l)
((Y (lambda (recfun)
(lambda (l)
(cond
((null? l) nil)
(t (or
(eq? (car l) a)
(recfun (cdr l))))))))
l)))

Step through the application (member-Y a l) where a is x and l is (y x).
Rewrite the functions rember, insertR, and subst2 in a similar mannar.