RxJava groupBy and scan

GroupScan.md

This code is the RxJava equivalent of the Spark updateStateByKey operation

GroupScan.scala

//Accumulate Strings with integer key
case class Sum(key: Int, sum: String ="") {
    def update(value: Char) = this.copy(sum = sum + value)
}

import rx.lang.scala._

//Source of Char
val s:Observable[Char] = _
 
// Accumulate characters into one of 4 buckets
s.groupBy { x => x % 4 } 
  .map { p => p._2.scan(Sum(p._1)) { (s: Sum, v: Char) => s.update(v) } }