Standard Data Types

Option

Rough definition

sealed trait Option[+A]
final case class Some[+A](x: A) extends Option[A]
case object None extends Option[Nothing]

Either

Either is a disjoint union of two types (also called Disjunction).

Rough definition

sealed trait Either[+E, +A]
case class Left[+E](value: E) extends Either[E, Nothing]
case class Right[+A](value: A) extends Either[Nothing, A]

Tuple

Tuples combine a fixed number of items together so that they can be passed around as whole. A tuple is immutable and can hold objects with different types, unlike an Array or List. Pairs and tuples of other arities are also algebraic data types.

Tuple

val p = ("Bob", 42)
// p: (String, Int) = (Bob,42)

// ("Bob", 42) is a syntactic sugar for:

Tuple2[String, Int]("Bob", 42)
// res0: (String, Int) = (Bob,42)

p._1
// res1: String = Bob

p._2
// res2: Int = 42

p match { case (a, b) => b }
// res3: Int = 42

List

Rough definition

sealed trait List[+A]
case object Nil extends List[Nothing]
case class Cons[+A](head: A, tail: List[A]) extends List[A]

Stream

Stream is also called lazy list.

Rough definition

sealed trait Stream[+A]
case object Empty extends Stream[Nothing]
case class Cons[+A](h: () => A, t: () => Stream[A]) extends Stream[A]