We covered some challenging concepts in this chapter. Type classes are also used in other functional programming languages, such as Haskell.
For convenience, the following table summarizes the type classes that we enumerated in this chapter:
Name | Method | Law(s) | Example(s) |
|
| Associativity | Option(1) |+| None |+| Option(2)// res5: Option[Int] = Some(3) |
|
| Identity | Vector(1,2,3).combineAll// res8: Int = 6 Vector("1", "2", "3").foldMap(s => (s,s.toInt))
// res10: (String, Int) = (123,6) |
|
| Identity,Composability | def square(x: Double): Double = x * x
def squareVector:
Vector[Double] => Vector[Double] =
Functor[Vector].lift(square)
squareVector(Vector(1, 2, 3))// res0: Vector[Double] = Vector(1.0, 4.0, 9.0)Vector("Functors", "are", "great")
.fproduct(_.length)
.toMap
// res2: Map[String,Int] = Map(Functors -> 8, //are -> 3, great -> 5) |
|
|