sbt/util/complete/EditDistance.scala

package sbt.complete

/** @author Paul Phillips*/
object EditDistance {
 /** Translated from the java version at
  *    http://www.merriampark.com/ld.htm
  *  which is declared to be public domain.
  */
 def levenshtein(s: String, t: String, insertCost: Int = 1, deleteCost: Int = 1, subCost: Int = 1, transposeCost: Int = 1, matchCost: Int = 0, transpositions: Boolean = false): Int = {
   val n = s.length
   val m = t.length
   if (n == 0) return m
   if (m == 0) return n

   val d = Array.ofDim[Int](n + 1, m + 1)
   0 to n foreach (x => d(x)(0) = x)
   0 to m foreach (x => d(0)(x) = x)

   for (i <- 1 to n ; val s_i = s(i - 1) ; j <- 1 to m) {
     val t_j   = t(j - 1)
     val cost  = if (s_i == t_j) matchCost else subCost
     val tcost  = if (s_i == t_j) matchCost else transposeCost
	  

     val c1 = d(i - 1)(j) + deleteCost
     val c2 = d(i)(j - 1) + insertCost
     val c3 = d(i - 1)(j - 1) + cost

     d(i)(j) = c1 min c2 min c3

     if (transpositions) {
       if (i > 1 && j > 1 && s(i - 1) == t(j - 2) && s(i - 2) == t(j - 1))
         d(i)(j) = d(i)(j) min (d(i - 2)(j - 2) + cost)
     }
   }

   d(n)(m)
 }
}