Generics

Type Parameters

Type parameters appear in brackets, such as [T].

pure func first_or[T](items: List[T], fallback: T) -> T:
    items.get(0).get_or(fallback)

Inferred Type Params

The call site usually determines generic types from arguments.

first_or([1, 2, 3], 0)
first_or(["a"], "fallback")

Generic Containers

List[T], Option[T], Result[T, E], Dict[K, V], and Set[T] are generic containers.

names: List[String] = []
maybe_score: Option[Int] = None

Reusable Helpers

A small generic helper should avoid extra constraints until it needs them.

pure func swap[A, B](pair: (A, B)) -> (B, A):
    (pair.1, pair.0)

Example

pure func first_or[T](items: List[T], fallback: T) -> T:
	match items.get(0):
		Some(value): value
		None: fallback


pure func swap[A, B](pair: (A, B)) -> (B, A):
	(pair.1, pair.0)


func main(args: List[String]) -> Void:
	print(first_or([1, 2, 3], 0).to_string())
	print(swap(("age", 42)).0.to_string())

Try It

blorp run generic-helpers.brp