Implementing Higher-Kinded Types in Scala
Starting with Scala 2.5, there’s a nifty feature called higher-kinded types.
- These types allow us to create a flexible ‘Collection‘ interface.
- Think of this interface as a toolbox that can work with various types of containers like lists, optionals, and arrays. When we use ‘F[]’, it means we’re talking about any type of container.
- It’s like saying ‘F’ can be a list, set, or any other container. how it works:
Example
1. Create a collection seqCollection that behaves like a sequence and provides operations:
var seqCollection = new Collection[Seq] {
override def wrap[A](a: A): Seq[A] = Seq(a)
override def first[B](b: Seq[B]): B = b.head
}
assert(seqCollection.wrap("Some values") == Seq("Some values"))
assert(seqCollection.first(Seq("Some values")) == "Some values")
So, with higher-kinded types, we’ve created a versatile ‘Collection’ that can work with any container type.
2. Define a collection seqCollection that emulates a sequence and implements operations:
var seqCollection = new Collection[Seq] {
override def wrap[A](a: A): Seq[A] = Seq(a)
override def first[B](b: Seq[B]): B = b.head
}
assertEquals(seqCollection.wrap("Some values"), Seq("Some values"))
assertEquals(seqCollection.first(Seq("Some values")), "Some values")
So, with higher-kinded types, we have created a ‘Collection’ that can work with any type of container.”
Higher-Kinded Types in Scala
This article focuses on discussing Higher-Kinded types in Scala.