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trying out different costs for edit distance

This commit is contained in:
Mark Harrah 2011-04-26 22:29:30 -04:00
parent 515386d973
commit 6c6eccea4f
2 changed files with 8 additions and 11 deletions
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9
main/Command.scala
View File

@ -127,14 +127,9 @@ object Command
if(suggested.isEmpty) "" else suggested.mkString(" (similar: ", ", ", ")")
}
def suggestions(a: String, bs: Seq[String], maxDistance: Int = 3, maxSuggestions: Int = 3): Seq[String] =
bs.map { b => (b, distance(a, b) ) } filter withinDistance(maxDistance, a) sortBy(_._2) take(maxSuggestions) map(_._1)
bs.map { b => (b, distance(a, b) ) } filter (_._2 <= maxDistance) sortBy(_._2) take(maxSuggestions) map(_._1)
def distance(a: String, b: String): Int =
EditDistance.levenshtein(a, b, insertCost = 1, deleteCost = 1, subCost = 2, transposeCost = 1, true)
def withinDistance(dist: Int, a: String)(ai: (String, Int)): Boolean =
{
val lengthBased = ( (ai._1.length min a.length) - 1 ) max 2
ai._2 <= (dist min lengthBased)
}
EditDistance.levenshtein(a, b, insertCost = 1, deleteCost = 1, subCost = 2, transposeCost = 1, matchCost = -1, true)
}
trait Help

10
util/complete/EditDistance.scala
View File

@ -6,7 +6,7 @@ object EditDistance {
* http://www.merriampark.com/ld.htm
* which is declared to be public domain.
*/
def levenshtein(s: String, t: String, insertCost: Int, deleteCost: Int, subCost: Int, transposeCost: Int, transpositions: Boolean = false): Int = {
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
@ -18,17 +18,19 @@ object EditDistance {
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) 0 else 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*subCost
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*transposeCost)
d(i)(j) = d(i)(j) min (d(i - 2)(j - 2) + cost)
}
}