Showing code from Functional Programming in Scala Book Code

NoReverseFoldright.scala

  /* 
  Taken from https://github.com/fpinscala/fpinscala/blob/master/answers/src/main/scala/fpinscala/datastructures/List.scala#L159
  
  This code is not mine - I only posted it here to share it.  It is part of the answer key solutions from http://www.manning.com/bjarnason/
  
  Paul Chiusano is one of the authors and has posted on topics such as Scala's limited type inferecing:
  http://pchiusano.blogspot.com/2011/05/making-most-of-scalas-extremely-limited.html
  
  */
  
  @annotation.tailrec
  def foldLeft[A,B](l: List[A], z: B)(f: (B, A) => B): B = l match {
    case Nil => z
    case Cons(h,t) => foldLeft(t, f(z,h))(f)
  }

  def foldRightViaFoldLeft_NoReverse[A,B](ls: List[A], z: B)(f: (A,B) => B): B = 
    foldLeft(ls, (b:B) => b) ((g,a) => b => g(f(a,b))) (z)