This homework has to do with mupl (a Made Up Programming Language). mupl programs are written directly in Racket by using the constructors defined by the structs here:

(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) 

here is the function I'm asking about

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

CodePudding user response：

It's one identifier, not two identifiers separated by an arrow – Scheme identifiers are not limited to alphanumerical characters and underscore like many other languages.

The conventional name of conversion functions from type A to type B is A->B, so racketlist->mupllist is a sensible name since it converts a Racket list into a mupl list.