More Scala fold examples

https://coderwall.com/p/4l73-a/scala-fold-foldleft-and-foldright



class Foo(val name: String, val age: Int, val sex: Symbol)

object Foo {
  def apply(name: String, age: Int, sex: Symbol) = new Foo(name, age, sex)
}

val fooList = Foo("Joe Smith", 25, 'male) :: Foo("Susan Jones", 43, 'female) :: Foo("Fred Flintstone", 37, 'male) :: Nil

val stringList = fooList.foldLeft(List[String]()) { (z, f) =>
  val title = f.sex match {
    case 'male => "Mr."
    case 'female => "Ms."
  }
  z :+ s"$title ${f.name}, ${f.age}"
}

scala> class Foo(val name: String, val age: Int, val sex: Symbol)

defined class Foo

warning: previously defined object Foo is not a companion to class Foo.

Companions must be defined together; you may wish to use :paste mode for this.

scala> 

scala> object Foo {

     |   def apply(name: String, age: Int, sex: Symbol) = new Foo(name, age, sex)

     | }

defined object Foo

warning: previously defined class Foo is not a companion to object Foo.

Companions must be defined together; you may wish to use :paste mode for this.

scala> 

scala> val fooList = Foo("Joe Smith", 25, 'male) :: Foo("Susan Jones", 43, 'female) :: Foo("Fred Flintstone", 37, 'male) :: Nil

fooList: List[Foo] = List(Foo@52d3542b, Foo@282afe91, Foo@7b1e1c25)

scala> 

scala> val stringList = fooList.foldLeft(List[String]()) { (z, f) =>

     |   val title = f.sex match {

     |     case 'male => "Mr."

     |     case 'female => "Ms."

     |   }

     |   z :+ s"$title ${f.name}, ${f.age}"

     | }

stringList: List[String] = List(Mr. Joe Smith, 25, Ms. Susan Jones, 43, Mr. Fred Flintstone, 37)