filling a list with a series of known elements

问题

Is there a quicker way to write the following code?

(list var1 var2 var3 var4 var5 ... var100)

Basically all the elements are variables with prefix "var".

回答1:

You can do this with a macro:

#lang racket
(require syntax/parse/define (for-syntax racket/syntax))
(define-simple-macro (varN-range var:id arg:number ...)
  #:with [varN ...]
  (for/list ([N (apply in-range (syntax->datum #'(arg ...)))])
    (format-id #'var "~a~a" #'var N))
  (list varN ...))

Using it:

> (define var1 "a")
> (define var2 "b")
> (define var3 "c")
> (define var4 "d")
> (define var5 "e")
> (varN-range var 1 6)
(list "a" "b" "c" "d" "e")

来源：https://stackoverflow.com/questions/63120915/filling-a-list-with-a-series-of-known-elements