Fold

Fold takes data in one format and gives it back to you in another.

val list = List(1, 2, 3, 4, 5)
val sum = list.fold(0)((x, y) => x + y)

fold, foldLeft, foldRight

• foldLeft()iterates from left to right
• foldRight()iterates from right to left
• fold()does not go in any particular order

  • start value must be a supertype of the object you are folding.

    e.g. Int is a supertype of List[Int]

  • start value must be neutral(not affect the result)