Scala Markov chainer for text.

gistfile1.txt

import scala.io.Source
import scala.util.Random

object Markov extends App {
  val outputLength: Int = args(0).toInt
  val prefixLength: Int = if (args.length > 1) args(1).toInt else 2

  val in = Source.fromInputStream(System.in).mkString("").split("""\s+""").toList

  val tokens = tokenize(in)

  val start = tokens.keys.toSeq(new Random().nextInt(tokens.keys.size))

  val out = generate(tokens, start.toStream)

  println(out.reverse.mkString(" "))

  def tokenize(in: List[String]) =
    in.sliding(prefixLength+1).toList.groupBy(chunk => chunk.take(prefixLength).reverse).map(p => p._1 -> p._2.map(_.last))

  def generate(tokens: Map[List[String], List[String]], accumulator: Stream[String]): Stream[String] = {
    val choices = tokens.getOrElse(accumulator.take(prefixLength).toList, Nil)

    if (accumulator.length == outputLength || choices.size == 0) accumulator
    else generate(tokens, choices(Random.nextInt(choices.size)) #:: accumulator)
  }
}