方案：创建一个程序产品，该产品将要求两个数字并计算其乘积

Question

Create a procedure product that will ask for two numbers and compute its product. If the product is greater than or equal to 20, your program will ask for a radius in order to compute the area of a circle; otherwise, the program will ask for the length and width to compute the area of a rectangle. If the product is zero, the program will display Invalid Inputs! The program should be implemented in at least two procedures.

help please? i have this

(define circle
  (lambda (radius)
    (* 3.14 (* radius radius)))

(define product
  (lambda (a b)
    (* a b))

Answer 1

You can "ask for two numbers" using read .

> (let ((a (read))) (format "You typed: ~a" a))
12
"You typed: 12"
> 

That coincidentally show you how to format output as well, though a read-through of the docs might still help with the finer points. Just remember to check if the return value is actually a number with number? , and the rest of your question should be pretty self-explanatory.