User-Defined Types

Beyond the built-in primitives and collections, mimas lets you define your own named types. There are two kinds, the algebraic product/sum pair:

• Structs – product types. A struct holds several values at once: a Player has a name, a score, and a position.
• Enums – sum types. An enum is exactly one of several shapes: a Shape is a circle, a rectangle, or a triangle, never more than one at a time.

Both gain behavior through impl blocks, and both can satisfy a pact to share an interface.