問題4.1

;; 4.1
;L->R
(define (list-of-values exps env)
  (if (no-operands? exps)
      '()
      (let ((val (eval (first-operand exps) env)))
        (cons val (list-of-values (rest-operands exps) env)))))

;R->L
(define (list-of-values exps env)
  (if (no-operands? exps)
      '()
      (let ((val (list-of-values (rest-operands exps) env)))
        (cons (eval (first-operand exps) env) val))))