Data commit

Task/Jaro-similarity/Elixir/jaro-similarity.elixir

@@ -0,0 +1,58 @@
+defmodule Jaro do
+  def distance(s, t) when is_binary(s) and is_binary(t), do:
+    distance(to_charlist(s), to_charlist(t))
+  def distance(x, x), do: 1.0
+  def distance(s, t) do
+    s_len = length(s)
+    t_len = length(t)
+    {s_matches, t_matches, matches} = matching(s, t, s_len, t_len)
+    if matches == 0 do
+      0.0
+    else
+      {k, transpositions} = transposition(s, t, s_matches, t_matches)
+      ((matches / s_len) +
+       (matches / t_len) +
+       ((matches - transpositions/2) / matches)) / 3
+    end
+  end
+
+  defp matching(s, t, s_len, t_len) do
+    match_distance = div(max(s_len, t_len), 2) - 1
+    ac0 = {List.duplicate(false, s_len), List.duplicate(false, t_len), 0}
+    Enum.reduce(0..s_len-1, ac0, fn i,acc ->
+      j_start = max(0, i-match_distance)
+      j_end = min(i+match_distance, t_len-1)
+      Enum.reduce_while(j_start..j_end, acc, fn j,{sm,tm,m} ->
+        if Enum.at(tm, j) or Enum.at(s, i) != Enum.at(t, j) do
+          {:cont, {sm, tm, m}}
+        else
+          {:halt, { List.replace_at(sm, i, true),
+                    List.replace_at(tm, j, true),
+                    m + 1 }}
+        end
+      end)
+    end)
+  end
+
+  defp transposition(s, t, s_matches, t_matches) do
+    Enum.reduce(0..length(s)-1, {0,0}, fn i,{k,transpositions} ->
+      if Enum.at(s_matches, i) do
+        k = k + (Enum.drop(t_matches, k)
+                 |> Enum.take_while(fn matche -> not matche end)
+                 |> length)
+        if Enum.at(s, i) == Enum.at(t, k), do: {k+1, transpositions},
+                                         else: {k+1, transpositions+1}
+      else
+        {k, transpositions}
+      end
+    end)
+  end
+end
+
+~w( MARTHA    MARHTA
+    DIXON     DICKSONX
+    JELLYFISH SMELLYFISH )c
+|> Enum.chunk(2)
+|> Enum.each(fn [s,t] ->
+     :io.format "jaro(~s, ~s) = ~.10f~n", [inspect(s), inspect(t), Jaro.distance(s, t)]
+   end)