这个函数中的箭头是做什么的？

Question

这项作业与 mupl（一种编造的编程语言）有关。多个程序通过使用此处结构定义的构造函数直接在 Racket 中编写：

(provide (all-defined-out)) ;; so we can put tests in a second file

;; definition of structures for MUPL programs - Do NOT change
(struct var  (string) #:transparent)  ;; a variable, e.g., (var "foo")
(struct int  (num)    #:transparent)  ;; a constant number, e.g., (int 17)
(struct add  (e1 e2)  #:transparent)  ;; add two expressions
(struct ifgreater (e1 e2 e3 e4)    #:transparent) ;; if e1 > e2 then e3 else e4
(struct fun  (nameopt formal body) #:transparent) ;; a recursive(?) 1-argument function
(struct call (funexp actual)       #:transparent) ;; function call
(struct mlet (var e body) #:transparent) ;; a local binding (let var = e in body) 
(struct apair (e1 e2)     #:transparent) ;; make a new pair
(struct fst  (e)    #:transparent) ;; get first part of a pair
(struct snd  (e)    #:transparent) ;; get second part of a pair
(struct aunit ()    #:transparent) ;; unit value -- good for ending a list
(struct isaunit (e) #:transparent) ;; evaluate to 1 if e is unit else 0

;; a closure is not in "source" programs but /is/ a MUPL value; it is what functions evaluate to
(struct closure (env fun) #:transparent)

这是我要问的函数

(define (racketlist->mupllist e)
  (cond [(null? e) (aunit)]
        [#t (apair (car e) (racketlist->mupllist (cdr e)))]))

Answer 1

它是一个标识符，而不是用箭头分隔的两个标识符 – 方案标识符不像许多其他语言那样仅限于字母数字字符和下划线。

从类型A到类型B的转换函数的常规名称是A->B，因此racketlist->mupllist是一个合理的名称，因为它将Racket列表转换为mupl列表。

这个函数中的箭头是做什么的？

what is the arrow doing in this function?

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