If you were familiar with Apache Spark, there are some array methods Spark and Scala have, but Ruby doesn't implement.

I make the expansion for ruby array for adding these methods:

  1. reduceByKey
  2. mapValues
  3. countByKey
  4. groupByKey
  5. sortByKey
  6. fold

Here is the sample code:

  require './groupMapReduce.rb'

  list = [["a",1], ["c",3], ["b",4], ["a",5]]

  p list.reduceByKey { |x,y| x+y }
  p list.mapValues { |x| x**2 }

The output:

  [["a", 6], ["c", 3], ["b", 4]]
  [["a", 1], ["c", 9], ["b", 16], ["a", 25]]