Enums

Pipefish lets you create your own enumerated types.

The script examples/enums.pf supplies an example of usage:

newtype

Suit = enum CLUBS, HEARTS, SPADES, DIAMONDS

Value = enum ACE, TWO, THREE, FOUR, FIVE, SIX, SEVEN,
          .. EIGHT, NINE, TEN, JACK, QUEEN, KING

Card = struct(value Value, suit Suit)

isBlack(suit Suit) : suit in {CLUBS, SPADES}

isBlack(card Card) : isBlack(card[suit])

The len function can be applied to enum types, e.g. len Suit is 4; and similarly enum types can be indexed by integers, e.g. Suit[2] is SPADES.

Let's put it through its paces in the REPL:

→ hub run "examples/enums.pf" as "Enums"
Starting script 'examples/enums.pf' as service 'Enums'.
Enums → Card ACE, CLUBS
Card with (value :: ACE, suit :: CLUBS)
Enums → isBlack CLUBS 
true
Enums → isBlack Card QUEEN, HEARTS 
false
Enums → type DIAMONDS 
Suit 
Enums → 

Note that two enums can't have a member in common.