This program calculates common factor for given numbers. The original use case is to find a possible resolution for pixel games that scale well with new screen resolutions (that's why I don't have any check and optimizations for big numbers and use simple brute force).

(define (fun1 l d)
    (if (apply = (map (lambda (x) (remainder x d)) l))
        (print d)))

(define (fun2 l)
    (do ((i 1 (+ i 1)))
        ((= i (apply min l)) i)
        (fun1 l i)))

(fun2 `(1080 720))

I'm learning lisp and scheme and want to know if there's any way to make this code more functional and lispy.

Also, I'm wondering if (apply = (1 2 3) is the right way to do it. I haven't found another way to force feed list of numbers to the = function or break numbers out of the list.


1 Answer 1


Scheme has a built-in function called gcd, which computes the greatest common divisor. You don't need to write your own version. (gcd 1080 720) returns 360.

One other thing I should mention is that, as a matter of style, you should prefer to use quote rather than backquote if you have nothing to unquote.


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