Merge pull request #120 from Jesin/feature/constructor-operatives

Operatives for working with enums

alicorn-utils.lua

@@ -303,4 +303,47 @@ function M.get_cursor_position(input_file, output_file)
 	return cursor_line, cursor_column
 end
 
+-- https://gist.github.com/Badgerati/3261142
+-- Returns the Levenshtein distance between the two given strings
+function M.levenshtein(str1, str2)
+	local len1 = string.len(str1)
+	local len2 = string.len(str2)
+	local matrix = {}
+	local cost = 0
+
+	-- quick cut-offs to save time
+	if len1 == 0 then
+		return len2
+	elseif len2 == 0 then
+		return len1
+	elseif str1 == str2 then
+		return 0
+	end
+
+	-- initialise the base matrix values
+	for i = 0, len1, 1 do
+		matrix[i] = {}
+		matrix[i][0] = i
+	end
+	for j = 0, len2, 1 do
+		matrix[0][j] = j
+	end
+
+	-- actual Levenshtein algorithm
+	for i = 1, len1, 1 do
+		for j = 1, len2, 1 do
+			if str1:byte(i) == str2:byte(j) then
+				cost = 0
+			else
+				cost = 1
+			end
+
+			matrix[i][j] = math.min(matrix[i - 1][j] + 1, matrix[i][j - 1] + 1, matrix[i - 1][j - 1] + cost)
+		end
+	end
+
+	-- return the last value - this is the Levenshtein distance
+	return matrix[len1][len2]
+end
+
 return M