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They look very much alike, don’t you think?

Such scenarios of deriving some value out of a collection of values are not unusual. Hence the solutions are also very similar. They are different mainly in two things: The initial accumulator value and How the accumulator is calculated as it is compared to every item. If only we could generalise the three functions above into a generic function where we could pass those 2 things, the code will be much simpler.

How do we implement these functions in Scala?

In Scala a built-in feature has been provided to cater for such scenarios, which is by using either foldLeft or foldRight. This is how those three functions are defined in Scala // For the sake of simplicity we are assuming that there are no 'null' contents in the list. // Initial accumulator value = 0. // The accumulator is recalculated with an addition in every iteration.

So basically foldRight is useless?

Yes. Most of the time. I have not yet found a scenario where it is better to use foldRight rather than foldLeft. And I don’t think this behaviour will change in the near future. It’s just the way it is natively structured in Scala.