Calculation of distance between strings

Function strdist(r,b,krk,cas) is intended for calculation of distance between strings.It computes Levenshtein and editor distances with use of Vagner-Fisher algorithm. Levenshtein distance is the minimal quantity of character substitutions, deletions and insertions for transformation of string r into string b. An editor distance is computed as Levenstein distance with substitutions weight of 2. You can also ignore a case.