我正在Dr.Racket中尝试使用R5RS。我想知道我工作的目录，并想更改该目录。当我在R5S5中尝试时，我得到以下错误：
Welcome to DrRacket, version 6.12 [3m].
Language: R5RS; memory limit: 128 MB.
> (current-directory)
. . current-directory: undefined;
cannot reference undefined identifier
>
然而，在Racket中运行同样的东西，我得到了目录。
Welcome to DrRacket, version 6.12 [3m].
Language: racket, with debugging; memory limit: 128 MB.
> (current-directory)
#<path:/home/shree/>
>
我无法在R5RS中找到current-directory的相应原语。
您可以从Racket:中要求东西
#lang r5rs
(#%require (only racket/base current-directory))
(display (current-directory))