Exercise 2.12 · 习题

Exercise 2.12: Define a constructor

make-center-percent that takes a center and a percentage tolerance and

produces the desired interval. You must also define a selector percent

that produces the percentage tolerance for a given interval. The center

selector is the same as the one shown above.

练习 2.12：定义构造函数 make-center-percent，它以中心值和百分比容差为参数，产生所需的区间。你还需要定义选择函数 percent，用于返回给定区间的百分比容差。center 选择函数与上面所示的相同。