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package com.rockymadden.stringmetric
object Tokenize {
sealed trait Tokenizer[A] {
def tokenize(a: A): Option[Array[A]]
}
sealed trait StringTokenizer extends Tokenizer[Array[Char]] {
def tokenize(a: String): Option[Array[String]]
}
object StringTokenizer {
val NGram = NGramTokenizer
def tokenizeWithNGram(n: Int)(charArray: Array[Char]) = NGram(n).tokenize(charArray)
}
final case class NGramTokenizer(n: Int) extends StringTokenizer {
override def tokenize(a: Array[Char]): Option[Array[Array[Char]]] = {
if (n <= 0) return None
if (a.length < n) None
else Some(sequence(a, Array.empty[Array[Char]], n))
}
override def tokenize(a: String): Option[Array[String]] = tokenize(a.toCharArray).map(_.map(_.mkString))
@annotation.tailrec
private val sequence: ((Array[Char], Array[Array[Char]], Int) => Array[Array[Char]]) = (i, o, n) =>
if (i.length <= n) o :+ i
else sequence(i.tail, o :+ i.take(n), n)
}
}
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