2016 Update

Task/LZW-compression/Elixir/lzw-compression.elixir

@@ -1,45 +1,36 @@
 defmodule LZW do
-  def encode(str), do: encode(to_char_list(str), init, 256, [])
+  @encode_map  Enum.into(0..255, Map.new, &{[&1],&1})
+  @decode_map  Enum.into(0..255, Map.new, &{&1,[&1]})
 
-  defp encode([h], d, _, out), do: Enum.reverse([Dict.get(d, [h]) | out])
+  def encode(str), do: encode(to_char_list(str), @encode_map, 256, [])
+
+  defp encode([h], d, _, out), do: Enum.reverse([d[[h]] | out])
   defp encode([h|t], d, free, out) do
-    val = Dict.get(d, [h])
+    val = d[[h]]
     find_match(t, [h], val, d, free, out)
   end
 
   defp find_match([h|t], l, lastval, d, free, out) do
-    case Dict.fetch(d, [h|l]) do
+    case Map.fetch(d, [h|l]) do
       {:ok, val} -> find_match(t, [h|l], val, d, free, out)
-      :error ->
-        d1 = Dict.put(d, [h|l], free)
-        encode([h|t], d1, free+1, [lastval | out])
+      :error     -> d1 = Map.put(d, [h|l], free)
+                    encode([h|t], d1, free+1, [lastval | out])
     end
   end
   defp find_match([], _, lastval, _, _, out), do: Enum.reverse([lastval | out])
 
-  defp init, do: init(255, Map.new)
-
-  defp init(0, d), do: d
-  defp init(n, d), do: init(n-1, Dict.put(d,[n],n))
-
   def decode([h|t]) do
-    d = init1(Map.new)
-    val = Dict.get(d, h)
-    decode(t, val, 256, d, val)
+    val = @decode_map[h]
+    decode(t, val, 256, @decode_map, val)
   end
 
   defp decode([], _, _, _, l), do: Enum.reverse(l) |> to_string
   defp decode([h|t], old, free, d, l) do
-    val = Dict.get(d, h)
+    val = d[h]
     add = [List.last(val) | old]
-    d1  = Dict.put(d, free, add)
+    d1  = Map.put(d, free, add)
     decode(t, val, free+1, d1, val++l)
   end
-
-  defp init1(d), do: init1(255, d)
-
-  defp init1(0, d), do: d
-  defp init1(n, d), do: init1(n-1, Dict.put(d, n, [n]))
 end
 
 str = "TOBEORNOTTOBEORTOBEORNOT"