Extração de NGram usando características empilháveis ​​em Scala

O código a seguir mostra os casos do padrão Stackable Traits , neste caso, para extrair Ngrams de um arquivo de entrada de frases

package com.github.ngram.extractor

object Boot extends App {
 val extractor = new SentenceAnalyzer
   with NGramExtraction
   with Unigrams
   with Bigrams
   with Trigrams

 val sentences =       Source.fromInputStream(getClass.getResourceAsStream("/input.txt")).getLines().toIterable
println(extractor.analyze(sentences))
}

trait NGrams { def arities: List[Int] }

trait NGramExtraction extends NGrams { override def arities = List.empty[Int] }
trait Unigrams extends NGrams { this: NGramExtraction => abstract override def arities = 1 :: super.arities }
trait Bigrams extends NGrams { this: NGramExtraction => abstract override def arities = 2 :: super.arities }
trait Trigrams extends NGrams { this: NGramExtraction => abstract override def arities = 3 :: super.arities }

trait SentenceAnalyzer {
  this: NGrams =>

  def analyze(sentences: Iterable[String]) = {
arities.flatMap { N =>
  val tokenizedSentence = sentences.map(_.split("\s").toList)
  tokenizedSentence.flatMap(_.sliding(N)).filter(_.size == N)
   }
 }