Exercise 3.18 · 习题

Exercise 3.18: Write a procedure that examines a

list and determines whether it contains a cycle, that is, whether a program

that tried to find the end of the list by taking successive cdrs would

go into an infinite loop. Exercise 3.13 constructed such lists.

练习 3.18：编写一个过程，检查一个表并判断其是否包含环，即：若某个程序试图通过连续取 cdr 来找到表的末尾，它是否会陷入无限循环。练习 3.13 构造了这样的表。