Undesired output in Racket - racket

Question

I'm working on a homework assignment and am a little bit confused as to what produced this output. Here is the code:
#lang racket
(define (my_calc calcType radius); define the function and set up the parameters
(define PI 3.1416); define PI
(cond ((and (= calcType 1) (positive? radius))); check to see whether the calc function is one and the radius is positive
((* 2 PI radius radius)); return the area of a circle
((and (= calcType 2) (positive? radius))); check to see whether the calc function is 2 and the radius is positive
((* (/ 4 3) PI radius radius radius)); return the volume of a sphere
(else #f); if calc function is not 1 or 2 or the radius is not positive, return false
)
)
(my_calc 1 10)
(my_calc 2 10)
(my_calc 0 1)
(my_calc 1 0)
and here is the output:
#t
628.32
6.2832
0
I have no idea why the first one would return true, it should return the area of a circle. There isn't even a return statement that would allow that. The second one seems to work just fine. The third one should produce false, but it produces the second answer divided by a hundred for some reason. And the 0 at the bottom is beyond me. Can anyone help me? Thank you.

Answer 1

Your first procedure in a cond case has to be the test expression followed by the result. See the documentation, https://docs.racket-lang.org/reference/if.html.
For example:
(cond
[; test expression
(and (= calcType 2) (positive? radius))
; following result
((* (/ 4 3) PI radius radius radius))]
[else whatever]
)
I would recommend using square brackets for each cond case for legibility.
In your case,
[(and (= calcType 1) (positive? radius))]
The test expression is (and (= calcType 1) (positive? radius)) but there is no following procedure.
You have the same problem for all of your cond cases. Good luck.