Earlier today I was writing a migration script in F# where I had to calculate the aspect ratio based on the given screen dimensions. This is one of those problems where I don’t even mind breaking my head over, but directly head over to Stackoverflow to find an accepted answer which I can just copy paste. Since I didn’t find an F# snippet I could use, I ported some JavaScript, and embedded the result below for future snippet hunters.

The aspectRatio function does two things:

1. Recursively find the greatest common divisor between the width and height
2. Divide the width and height by the greatest common divisor

let aspectRatio width height =
  let rec greatestCommonDivisor x y =
    match y with 
    | 0 -> x
    | _ -> greatestCommonDivisor y (x % y)

  let gcd = greatestCommonDivisor width height

  width / gcd, height / gcd
  
// > aspectRatio 1200 900;;
// val it : int * int = (4, 3)
// > aspectRatio 100 100;;
// val it : int * int = (1, 1)
// > aspectRatio 900 1200;;
// val it : int * int = (3, 4)