方案-使用申请 [英] Scheme - using apply

问题描述

我作为家庭作业接受了以下练习.我在上面坐了好几个小时都没有成功，所以别无选择，只能使用您的帮助.

I received the following exercise as homework. I sat on it for hours without any success, so I have no choice but to use your help.

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" 

推荐答案

这应该做到:

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

这篇关于方案-使用申请的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！