方案 - 使用 apply

Question

我收到了以下练习作为家庭作业。我在上面坐了几个小时都没有成功，所以我别无选择，只能求助于你。

示例：

(define m1 (cons "fixNumber" (lambda () 42)))

(define m3 (cons "add" (lambda (x y) (+ x y))))

(define myobj (create-obj (list m1 m2 m3)))

(myobj "fixNumber" '()) ;; => 42

(myobj "add" '(1 2)) ;; => 3

(myobj "myMethod" '()) ;; => "Error: no such method" 

Answer 1

应该这样做：

(define (create-obj mlist)
  (lambda (method parms)
    (let ((func (assoc method mlist)))
      (if func
          (apply (cdr func) parms)
          "Error: no such method"))))