2016 Update

Task/Generate-Chess960-starting-position/Elixir/generate-chess960-starting-position-1.elixir

@@ -0,0 +1,11 @@
+defmodule Chess960 do
+  @pieces   ~w(♔ ♕ ♘ ♘ ♗ ♗ ♖ ♖)             # ~w(K Q N N B B R R)
+  @regexes  [~r/♗(..)*♗/, ~r/♖.*♔.*♖/]        # [~r/B(..)*B/, ~r/R.*K.*R/]
+
+  def shuffle do
+    row = Enum.shuffle(@pieces) |> Enum.join
+    if Enum.all?(@regexes, &Regex.match?(&1, row)), do: row, else: shuffle
+  end
+end
+
+Enum.each(1..5, fn _ -> IO.puts Chess960.shuffle end)

Task/Generate-Chess960-starting-position/Elixir/generate-chess960-starting-position-2.elixir

@@ -0,0 +1,13 @@
+defmodule Chess960 do
+  def construct do
+    row = Enum.reduce(~w[♕ ♘ ♘], ~w[♖ ♔ ♖], fn piece,acc ->
+            List.insert_at(acc, :rand.uniform(length(acc)+1)-1, piece)
+          end)
+    [Enum.random([0, 2, 4, 6]), Enum.random([1, 3, 5, 7])]
+    |> Enum.sort
+    |> Enum.reduce(row, fn pos,acc -> List.insert_at(acc, pos, "♗") end)
+    |> Enum.join
+  end
+end
+
+Enum.each(1..5, fn _ -> IO.puts Chess960.construct end)

Task/Generate-Chess960-starting-position/Elixir/generate-chess960-starting-position-3.elixir

@@ -0,0 +1,31 @@
+defmodule Chess960 do
+  @krn  ~w(NNRKR NRNKR NRKNR NRKRN RNNKR RNKNR RNKRN RKNNR RKNRN RKRNN)
+
+  def start_position, do: start_position(:rand.uniform(960)-1)
+
+  def start_position(id) do
+    pos = List.duplicate(nil, 8)
+    q = div(id, 4)
+    r = rem(id, 4)
+    pos = List.replace_at(pos, r * 2 + 1, "B")
+    q = div(q, 4)
+    r = rem(q, 4)
+    pos = List.replace_at(pos, r * 2, "B")
+    q = div(q, 6)
+    r = rem(q, 6)
+    i = Enum.reject(0..7, &Enum.at(pos,&1)) |> Enum.at(r)
+    pos = List.replace_at(pos, i, "Q")
+    krn = Enum.at(@krn, q) |> String.codepoints
+    Enum.reject(0..7, &Enum.at(pos,&1))
+    |> Enum.zip(krn)
+    |> Enum.reduce(pos, fn {i,x},acc -> List.replace_at(acc,i,x) end)
+    |> Enum.join
+  end
+end
+
+IO.puts "Generate Start Position from ID number"
+Enum.each([0,518,959], fn id ->
+  :io.format "~3w : ~s~n", [id, Chess960.start_position(id)]
+end)
+IO.puts "\nGenerate random Start Position"
+Enum.each(1..5, fn _ -> IO.puts Chess960.start_position end)