1 files changed, 74 insertions, 0 deletions
diff --git a/bin/subtle-contrib/ruby/levenshtein.rb b/bin/subtle-contrib/ruby/levenshtein.rb
new file mode 100644
index 0000000..6122149
--- /dev/null
+++ b/bin/subtle-contrib/ruby/levenshtein.rb
@@ -0,0 +1,74 @@
+#
+# @file Calculate Levenshtein distance
+#
+# @copyright (c) 2010-2011, Christoph Kappel <unexist@dorfelite.net>
+# @version $Id$
+#
+# This program can be distributed under the terms of the GNU GPLv2.
+# See the file COPYING for details.
+#
+
+module Levenshtein
+  MAX_LENGTH = 255
+
+   ## distance {{{
+   # @brief Calculate the Levenshtein Distance
+   # @param [String]  s1        First string
+   # @param [String]  s2        Second string
+   # @param [Fixnum]  cost_ins  Cost for insertion
+   # @param [Fixnum]  cost_rep  Cost for replace
+   # @param [Fixnum]  cost_del  Cost for deletion
+   # @param [Array]   a1        First array
+   # @param [Array]   a2        Second array
+   # @raise [String]  Error
+   # @return [Fixnum] Calculated distance
+   ##
+
+  def self.distance(s1, s2, cost_ins = 1, cost_rep = 1,
+      cost_del = 1, a1 = nil, a2 = nil)
+    # Step 1: Check string length
+    l1 = s1.length
+    l2 = s2.length
+
+    # Check length
+    return l2 * cost_ins if 0 == l1
+    return l1 * cost_del if 0 == l2
+
+    raise "Max length" if l1 > MAX_LENGTH || l2 > MAX_LENGTH
+
+    # Step 2: Create and init arrays
+    p1 = a1 || Array.new(l2 + 1, 0)
+    p2 = a2 || Array.new(l2 + 1, 0)
+
+    (0..l2).each { |i| p1[i] = i * cost_ins }
+
+    # Step 3: Iterate over string s1
+    (0..(l1 - 1)).each do |i|
+      p2[0] = p1[0] + cost_del
+
+      # Step 4: Iterate over string s2
+      (0..(l2 - 1)).each do |j|
+        # Step 5: Get cost
+        c0 = p1[j] + ((s1[i] == s2[j]) ? 0 : cost_rep)
+        c1 = p1[j + 1] + cost_del
+        c0 = c1 if c1 < c0
+
+        c2 = p2[j] + cost_ins
+        c0 = c2 if c2 < c0
+
+        # Step 6: Store min value in matrix
+        p2[j + 1] = c0
+      end
+
+      # Swap arrays
+      tmp = p1
+      p1  = p2
+      p2  = tmp
+    end
+
+    # Step 7: Return distance
+    c0 = p1[l2]
+
+    c0
+  end # }}}
+end # }}}