Exercise 4.10 · 习题

Exercise 4.10: By using data abstraction, we

were able to write an eval procedure that is independent of the

particular syntax of the language to be evaluated. To illustrate this, design

and implement a new syntax for Scheme by modifying the procedures in this

section, without changing eval or apply.

练习 4.10：通过使用数据抽象，我们得以编写一个与待求值语言的具体语法无关的 eval 过程。为了说明这一点，请通过修改本节中的各个过程（而不改变 eval 或 apply），为 Scheme 设计并实现一套新的语法。