Slide 12 of 37

Declared types

A struct

type User {
	id:   Int
	name: Str
}

proc main(): void {
	u := User(1, "ada")
	echo u.name
}

A tagged union

type Shape {
	Circle    { radius: Int }
	Rectangle { width: Int, height: Int }
	Point
}

proc main(): void {
	p := Shape.Circle(5)
	echo p
}

A type with no variants is a struct; with variants, a tagged union. A field declared outside any variant is added to every variant. A value is built by calling the type or the variant: User(1, "ada"), Shape.Circle(5). There is no subtyping and no interface — a variant is a way of building and matching a union, not a type of its own.

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