Exercise 4.14 · 习题

Exercise 4.14: Eva Lu Ator and Louis Reasoner

are each experimenting with the metacircular evaluator. Eva types in the

definition of map, and runs some test programs that use it. They work

fine. Louis, in contrast, has installed the system version of map as a

primitive for the metacircular evaluator. When he tries it, things go terribly

wrong. Explain why Louis’s map fails even though Eva’s works.

练习 4.14：Eva Lu Ator 和 Louis Reasoner 各自在用元循环求值器做实验。Eva 键入了 map 的定义并运行了一些使用它的测试程序，一切正常。Louis 则不同，他将系统版本的 map 作为基本过程安装到元循环求值器中。当他尝试使用时，事情出了严重的错误。请解释为什么 Louis 的 map 会失败，而 Eva 的却能正常工作。