code: func Distance(str1, str2 string, p *Params) int {
  	if p == nil {
  		p = defaultParams
  	}
  	dist, _, _ := Calculate([]rune(str1), []rune(str2), p.maxCost, p.insCost, p.subCost, p.delCost)
  	return dist
  }
docs: // Distance returns the Levenshtein distance between str1 and str2, using the
  // default or provided cost values. Pass nil for the third argument to use the
  // default cost of 1 for all three operations, with no maximum.