Digital Moose Tracks

When I first learned about active patterns in F# I thought they were pretty great.  Then I saw you this F# video and learned you can patterns as function parameters.  This lets you do stuff like the following. (note I stole the example from this F# video)

open System.Drawing

let (|RGB|) (color : Color) = (color.R, color.G, color.B)

let printRGB (RGB(r, g, b)) =
    printfn "%d, %d, %d" r g b

printRGB Color.Red

I find this especially cool because I often have a wrapper function to do this sort of data transformation and this is far more elegant.