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Type Definitions

Sometimes it can be useful to define a name to refer to a longer type (when that type is long or needs to be referred to often).

type MyTriplet = (Int, Int, Int);
fun makeTriplet(): MyTriplet { (0, 0, 0) }

Things become more interesting within a class. A class can define a type, and later redefine it in one of its children.

base class MyUser{name: String, age: Int} {
  type ID;
  static fun load(this::ID): this;
}

class IntKeyedUser{} {
  type ID = Int;
  static fun load(key: this::ID): this {
    ...
  }
}
class StringKeyedUser{} {
  type ID = String;
  static fun load(key: this::ID): this {
    ...
  }
}

But why bother? After all, we could have defined the function load with the type Int directly and call it a day, right? Well, that feature becomes particularly interesting when coupled with deferred methods.