方案初学者问题
我试图在 Dr.Scheme 中添加以下语句：
{with {x {+ 5 5}} {+ xx}}
但出现错误：
expand: unbound identifier in module in: with
任何人都可以帮助我吗？谢谢。
I am trying to put the following statement in Dr.Scheme:
{with {x {+ 5 5}} {+ x x}}
but I got an error:
expand: unbound identifier in module in: with
anyone could help me?Thanks.
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您正在学习一些基于 PLAI 的课程，并且您将您正在使用的语言（方案）与您正在实现的语言（WAE 或扩展之一）混淆了。这两者是非常不同的东西，本书在后者中使用花括号以避免混淆。
我可以根据多次教授这门课的经验告诉你，这是一种危险的混乱，你越早澄清越好。如果你把它抛在脑后，不久的将来事情可能会变得更加混乱。因此，花一些时间研究两种语言之间的差异，并确保您知道本书的哪些部分讨论哪种语言。
You're taking some PLAI-based course, and you confuse the language that you're working in (Scheme) with the language that you're implementing (WAE, or one of the extensions). These two are very different things, and the book uses curly braces in the latter to avoid confusion.
I can tell you from experience of teaching this class a number of times that it's a dangerous confusion, and the sooner you clarify things the better. If you leave it behind things might get more confusing in the near future. So spend some time on the differences between the two languages, and make sure that you know which parts of the book talk about which language.
您是否想这样做：
如果您能说出您正在尝试使用哪种方案的方言，这将非常有帮助。
Are you trying to do this:
It would be really helpful if you could say what dialect of Scheme you are trying to use.