Vfrdtyky

I'm using a tutorial from Rosetta Code to calculate Levenshtein distance. It seems their code is in Swift2 so I get this error Binary operator '+' cannot be applied to operands of type '[Int]' and 'Repeated<String.CharacterView>' when doing this: var cur = [i + 2] + empty where let empty = repeatElement(s, count: 0). How can I go about this?

There were a couple of changes to make.

• The construction of the Array empty.


• enumerate() is now enumerated()


• successor() doesn't exist anymore so I replaced it with +1

So the function is now

Swift 4:

func levDis(_ w1: String, _ w2: String) -> Int {

    let empty = [Int](repeating:0, count: w2.count)

    var last = [Int](0...w2.count)



    for (i, char1) in w1.enumerated() {

        var cur = [i + 1] + empty

        for (j, char2) in w2.enumerated() {

            cur[j + 1] = char1 == char2 ? last[j] : min(last[j], last[j + 1], cur[j]) + 1

        }

        last = cur

    }

    return last.last!

}

Swift 3:

func levDis(w1: String, w2: String) -> Int {



    let (t, s) = (w1.characters, w2.characters)



    let empty = Array<Int>(repeating:0, count: s.count)

    var last = [Int](0...s.count)



    for (i, tLett) in t.enumerated() {

        var cur = [i + 1] + empty

        for (j, sLett) in s.enumerated() {

            cur[j + 1] = tLett == sLett ? last[j] : min(last[j], last[j + 1], cur[j])+1

        }

        last = cur

    }

    return last.last!

}

Updated and improved answer to Swift 4, based on @Spads answer.

extension String {

    func levenshteinDistanceScore(to string: String, ignoreCase: Bool = true, trimWhiteSpacesAndNewLines: Bool = true) -> Float {



        var firstString = self

        var secondString = string   



        if ignoreCase {

            firstString = firstString.lowercased()

            secondString = secondString.lowercased()

        }

        if trimWhiteSpacesAndNewLines {

            firstString = firstString.trimmingCharacters(in: .whitespacesAndNewlines)

            secondString = secondString.trimmingCharacters(in: .whitespacesAndNewlines)

        }



        let empty = [Int](repeating:0, count: secondString.count)

        var last = [Int](0...secondString.count)



        for (i, tLett) in firstString.enumerated() {

            var cur = [i + 1] + empty

            for (j, sLett) in secondString.enumerated() {

                cur[j + 1] = tLett == sLett ? last[j] : Swift.min(last[j], last[j + 1], cur[j])+1

            }

            last = cur

        }



        // maximum string length between the two

        let lowestScore = max(firstString.count, secondString.count)



        if let validDistance = last.last {

            return  1 - (Float(validDistance) / Float(lowestScore))

        }



        return 0.0

    }

}



infix operator =~

func =~(string: String, otherString: String) -> Bool {

    return string.levenshteinDistanceScore(to: otherString) >= 0.85

}

func ~=(string: String, otherString: String) -> Bool {

    return string.levenshteinDistanceScore(to: otherString) >= 0.85 

}