How to use variable names with the Scala ‘foldLeft’ method

As a little Scala fold/reduce example, here’s a quick example of how to use variable names with the Scala foldLeft method:

val pSum = movies.foldLeft(0.0)((accum, element) => 
    accum + p1Movies(element) * p2Movies(element)

In this example the variable movies is a Seq, and the variables p1Movies and p2Movies are Map objects.

If you know a little about how to use foldLeft, I hope the variable names accum (short for accumulator) and element are meaningful. (Jamie Allen writes that he uses the name current for what I call element.)

Most Scala foldLeft, reduce, reduceLeft, reduceRight examples show how to use underscores instead of variable names, so I wanted to make a note of how to use variable names.

If you also wanted to see how to use variable names with these Scala methods, I hope this example is helpful.

Another example

Here’s an example of how to write a “sum” algorithm using variable names with reduce:

def sum(list: List[Int]): Int = list.reduce((x,y) => x + y)