(assign evalable-ld-printingp nil)

(defun mem (e x)
  (if (endp x)
      nil
      (if (equal e (car x))
          t
          (mem e (cdr x)))))

(defun app (x y)
  (if (endp x)
      y
      (cons (car x)
            (app (cdr x) y))))

(defun cons? (e x)
  
; Add element e to list x if it is not already
; there; else just return x.
  
  (if (mem e x)
      x
      (cons e x)))

(defun app? (x y)
  
; Like app but does not introduce
; duplicate elements.
  
  (if (endp x)
      y
      (cons? (car x)
             (app? (cdr x) y))))

(quote (end of example))

(defun insert (e x)
  (if (endp x)
      (cons e x)
      (if (lexorder e (car x))
          (cons e x)
          (cons (car x)
                (insert e (cdr x))))))

(insert 'susan '(joan mike tom ursalla))

(defun isort (x)
  (if (endp x)
      nil
      (insert (car x)
              (isort (cdr x)))))

(isort '(susan ursalla joan tom mike))