如何评估球拍中的弦 [英] How to eval strings in racket

问题描述

我试图了解如何获取eval函数以读取字符串并评估字符串内部的内容.

I'm trying to understand how to get the eval function to read a string and evaluate the content that's inside the string.

目前我知道

> (eval '(+ 1 2))
   3

但是我对球拍的使用并不了解.因此，目前我正在尝试获取它，以便可以执行此操作:

but I'm not that knowledgeable with the use of racket. So at the moment I'm trying to get it so that I can do this:

> (eval "(+ 1 2)")
   3

任何建议或指向有用资源的链接都将不胜感激.

Any advice or links to useful resources would be appreciated.

推荐答案

您要与open-input-string一起使用read.像这样:

You want to use read together with open-input-string. Like so:

-> (eval (read (open-input-string "(+ 1 2)")))
3

您还可以使用with-input-from-string:

-> (with-input-from-string "(+ 1 2)"
     (lambda () (eval (read))))
3

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