unison/unison-src/sheepshead.u

type Suit = Club | Spade | Heart | Diamond
type Card = Card Rank Suit
type Rank = A | K | Q | J | _10 | _9 | _8 | _7
type NonEmpty a = NonEmpty a [a]

use Rank A K Q J _10 _9 _8 _7
use Suit Club Spade Heart Diamond
use NonEmpty NonEmpty
use Optional Some None

namespace Suit where
  all = [Club, Spade, Heart, Diamond]

namespace Rank where
  all = [A, _10, K, Q, J, _9, _8, _7]
  points = cases
    A -> 11
    _10 -> 10
    K -> 4
    Q -> 3
    J -> 2
    _ -> 0
  toText = cases
    A -> "A"
    K -> "K"
    Q -> "Q"
    J -> "J"
    _10 -> "10"
    _9 -> "9"
    _8 -> "8"
    _7 -> "7"

namespace NonEmpty where
  toList = cases
    NonEmpty h t -> Sequence.cons h t
  fromList : [a] -> Optional (NonEmpty a)
  fromList l = match Sequence.at 0 l with
    None -> None
    Some a -> Some (NonEmpty a (Sequence.drop 1 l))