Exercise 1.4 · 习题

Exercise 1.4: Observe that our model of
evaluation allows for combinations whose operators are compound expressions.
Use this observation to describe the behavior of the following procedure:

(define (a-plus-abs-b a b)

((if (> b 0) + -) a b))

练习 1.4：观察到我们的求值模型允许运算符是复合表达式的组合式。利用这一观察，描述以下过程的行为：

(define (a-plus-abs-b a b)
((if (> b 0) + -) a b))