1 files changed, 12 insertions, 25 deletions
diff --git a/core/source/main/scala/com/rockymadden/stringmetric/similarity/NGramMetric.scala b/core/source/main/scala/com/rockymadden/stringmetric/similarity/NGramMetric.scala
index e74e8eb..8025f38 100755
--- a/core/source/main/scala/com/rockymadden/stringmetric/similarity/NGramMetric.scala
+++ b/core/source/main/scala/com/rockymadden/stringmetric/similarity/NGramMetric.scala
@@ -1,21 +1,19 @@
 package com.rockymadden.stringmetric.similarity
 
-import com.rockymadden.stringmetric.{StringMetric, MatchTuple, StringFilter}
-import com.rockymadden.stringmetric.tokenization.NGramTokenizer
-import scala.math
+import com.rockymadden.stringmetric.Metric.StringMetricLike
 
-/** An implementation of the N-Gram metric. */
-class NGramMetric extends StringMetric[Int, Double] { this: StringFilter =>
-	final override def compare(charArray1: Array[Char], charArray2: Array[Char])(implicit n: Int): Option[Double] = {
-		if (n <= 0) throw new IllegalArgumentException("Expected valid n.")
+final case class NGramMetric(private val n: Int) extends StringMetricLike[Double] {
+	import com.rockymadden.stringmetric.MatchTuple
+	import com.rockymadden.stringmetric.tokenization.NGramTokenizer
+	import scala.math
 
-		val fca1 = filter(charArray1)
-		lazy val fca2 = filter(charArray2)
+	override def compare(a: Array[Char], b: Array[Char]): Option[Double] = {
+		if (n <= 0) return None
 
-		if (fca1.length < n || fca2.length < n) None // Because length is less than n, it is not possible to compare.
-		else if (fca1.sameElements(fca2)) Some(1d)
-		else NGramTokenizer.tokenize(fca1)(n).flatMap { ca1bg =>
-			NGramTokenizer.tokenize(fca2)(n).map { ca2bg =>
+		if (a.length < n || b.length < n) None // Because length is less than n, it is not possible to compare.
+		else if (a.sameElements(b)) Some(1d)
+		else NGramTokenizer(n).tokenize(a).flatMap { ca1bg =>
+			NGramTokenizer(n).tokenize(b).map { ca2bg =>
 				val ms = scoreMatches((ca1bg.map(_.mkString), ca2bg.map(_.mkString)))
 
 				ms.toDouble / math.max(ca1bg.length, ca2bg.length)
@@ -23,18 +21,7 @@ class NGramMetric extends StringMetric[Int, Double] { this: StringFilter =>
 		}
 	}
 
-	final override def compare(string1: String, string2: String)(implicit n: Int): Option[Double] =
-		compare(string1.toCharArray, string2.toCharArray)(n)
+	override def compare(a: String, b: String): Option[Double] = compare(a.toCharArray, b.toCharArray)
 
 	private[this] def scoreMatches(mt: MatchTuple[String]) = mt._1.intersect(mt._2).length
 }
-
-object NGramMetric {
-	private lazy val self = apply()
-
-	def apply(): NGramMetric = new NGramMetric with StringFilter
-
-	def compare(charArray1: Array[Char], charArray2: Array[Char])(n: Int) = self.compare(charArray1, charArray2)(n)
-
-	def compare(string1: String, string2: String)(n: Int) = self.compare(string1, string2)(n)
-}