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Enums

Enums define a set of named variants under a single type

declaration​

declare them like this

enum Color {
  Red
  Blue
  Green
}

here each variant belongs to the Color type

using variants​

you can use enum variants as values using member expressions like this

egg c = Color.Red

since enums define a new type you can use them in type annotation

egg c Color = Color.Blue

enums as types​

since Enums are first-class types you can use them in things like function parameters too

fun foo(c Color) {
  // ...
}

foo(Color.Blue)

some notes:​

  • Enum variant names must be unique within the enum
  • Enums cannot be redeclared
  • Accessing an unknown variant is a runtime error