Enums

Enums let a value be one of several named variants.

type Language := enum {
  FRENCH : FrenchData,
  ENGLISH : int,
  SPANISH,
  ARABIC : <Language, Language>
};

Each variant may carry different kinds of data:

• no payload at all, like SPANISH
• a single value, like ENGLISH : int
• a struct payload, like FRENCH : FrenchData
• a tuple payload, like ARABIC : <Language, Language>

You create enum values by naming the variant.

let english : Language = Language.ENGLISH : 6;
let french := Language.FRENCH : FrenchData { data : 10, code : 5 };
let spanish := Language.SPANISH;

Enums are most powerful when combined with pattern matching.

match english {
  .ENGLISH : level => print(level),
  .SPANISH => print("spanish"),
  _ => print("other")
};

Payloads can be destructured directly in the match arm.

match french {
  .FRENCH : {data: d, code: c} => print(d + c),
  _ => print("other")
};

Tuple payloads can also be destructured.

type PairEnum := enum { Normal : Pair, Tuple : <int, int> };

match PairEnum.Tuple : (10, 30) {
  .Tuple : (left, right) => print(left + right),
  _ => {}
};

Use enums when a value can take several different shapes, and each shape should be handled explicitly.