Enums

Enums define a type with a fixed set of named values.

Basic Enums

enum Color
    Red
    Green
    Blue
fin enum.

@primary = Color#Red

Enums with Values

Enums can carry associated data:

enum Shape
    Circle(radius: Float)
    Rectangle(width: Float, height: Float)
    Triangle(base: Float, height: Float)
fin enum.

@circle = Shape#Circle(radius: 5.0)
@rect = Shape#Rectangle(width: 10.0, height: 20.0)

Enum Actions

Define actions on enums:

enum Shape
    Circle(radius: Float)
    Rectangle(width: Float, height: Float)
fin enum.

impl Shape
    action area(@self: Shape) -> Float
        match @self
            when Circle then
                return 3.14159 * @self#radius * @self#radius
            when Rectangle then
                return @self#width * @self#height
        fin match.
    fin action.
fin impl.

@circle = Shape#Circle(radius: 5.0)
write(@circle#area())  @// 78.53975

Enum with Flags

Bit flag enums:

flag enum Permissions
    Read    = 0x01
    Write   = 0x02
    Execute = 0x04
fin enum.

@perms = Permissions#Read | Permissions#Write

Enum Iteration

Iterate over all enum values:

for @color in Color#values()
    write(@color#name)
fin for.

Enum from String

Parse enum from string:

@color = Color#from_string("Red")

Result Enum

The built-in Result type is an enum:

enum Result<T, E>
    ok(value: T)
    err(error: E)
fin enum.

Option Enum

The built-in Option type:

enum Option<T>
    some(value: T)
    none
fin enum.

Exhaustive Matching

Match must handle all enum variants:

match @shape
    when Circle then handle_circle(@shape)
    when Rectangle then handle_rect(@shape)
    when Triangle then handle_triangle(@shape)
fin match.

Missing a variant is a compile error.

Enum Visibility

pub enum Status
    Active
    Inactive
    Pending
fin enum.

Generic Enums

enum Either<L, R>
    left(value: L)
    right(value: R)
fin enum.

@result = Either<String, Int>#left("error")

Enum Serialization

@json = @shape#to_json()
@shape = Shape#from_json(@json)

Next Steps

Learn about Collections for arrays, maps, and sets.