anchor.diff:  (defun rest-cond-clauses (exp)
     (cdr exp))
   
  +(defun cond-clause-recipient-p (exp)
  +  (eq (cadr exp) '=>))
  +
   (defun cond-clause-pred (clause)
     (car clause))
   
   (defun cond-clause-exps (clause)
     (cdr clause))
  +
  +(defun cond-clause-recipient (clause)
  +  (caddr clause))
   
   (defun else-clause-p (clause)
     (tagged-list-p clause 'else))
  
positive.code: 	     (if (null clauses)
  		 'false
  		 (let* ((clause (first-cond-clause clauses))
  			(pred (cond-clause-pred clause))
  			(exps (cond-clause-exps clause)))
  		   (if (eq pred 'else)
  		       `(begin ,@exps)
  		       `(if ,pred
  			    (begin ,@exps)
  			    ,(iter (rest-cond-clauses clauses))))))))
      (iter (cdr exp))))
  
  ;; (cond (pred1 exp1 ...)
  
negative.code:     (loop
        (fresh-line)
        (format t "LISP> ")
        (t-print (t-eval (read) env))
        ;; (handler-case
        ;; 	  (t-print (t-eval (read) env))
        ;; 	(error (e) (princ e))))))
        )))
  