[racket] in praise of if's mandatory else clause

Hey, here is what I had written: see purpose statement: 

;; N -> Boolean 
;; simplistic definition 
(define (leap-year? y)
  (= (remainder y 4) 0))


On May 31, 2011, at 8:55 AM, Pierpaolo Bernardi wrote:

> On Tue, May 31, 2011 at 07:07, Richard Cleis <rcleis at mac.com> wrote:
>> Buggy loops can also be avoided by reducing the problem.  These leap-year cases are less troubling if the function that really matters is used: the days in a given year.
>> 
>> (define (days-in-year year) (if (= 0 (remainder year 4)) 366 365))
> 
> Please.  I understand that it is just an example, and that you most
> certainly know the correct definition of a leap year, but someone might
> not know it and blindly copy this function somewhere where it can cause
> harm.
> 
> Kids, use this one instead:
> 
> (define (leap-year? year)
>  (and (zero? (modulo year 4))
>       (or (not (zero? (modulo year 100)))
>           (zero? (modulo year 400)))))
> 
> (define (days-in-year year)
>  (if (leap-year? year)
>    366
>    365))
> 
> 
> 8^)
> 
> P.