FoldLeft using FoldRight in scala

Question

While going through Functional Programming in Scala, I came across this question:

Can you right foldLeft in terms of foldRight? How about the other way

Answer 1

That code is chaining several function objects together, one function for each element in the list. Here is an example that shows that more clearly.

val f = (a: Int, b: Int) => a+b
val list = List(2,3,4)
println(list.foldLeft(1)(f))

val f1 = (b: Int) => f(b, 2)
val f2 = (b: Int) => f(b, 3)
val f3 = (b: Int) => f(b, 4)
val f4 = (b: Int) => b

val ftotal = f1 andThen f2 andThen f3 andThen f4
println(ftotal(1))

You can imagine that as a linked list of function objects. When you pass in a value it "flows" through all the functions. It's a little like dataflow programming.