F# modeling playing cards

Question

I am trying to represent standard playing cards in F#. My goal is to implement a clone of Microsoft Solitaire (the one that comes with Windows) , a game in which Cards\' Sui

Answer 1

Since Color can always be inferred from Suit, there's no reason to model it explicitly; you'll want to make illegal states unrepresentable.

You can still get a nice programming experience out of your model, and have a nice way of modelling colour, using an Active Pattern:

type Suit =
    | Diamonds
    | Hearts
    | Clubs
    | Spades

let (|Red|Black|) suit =
    match suit with
    | Diamonds | Hearts -> Red
    | Clubs | Spades -> Black

This would enable you to pattern match on Suit, like this inane example:

let printColor card =
    match card.Suit with
    | Red -> "Red"
    | Black -> "Black"

Usage example from FSI:

> printColor { Suit = Spades; Face = Ace };;
val it : string = "Black"
> printColor { Suit = Diamonds; Face = King };;
val it : string = "Red"