Partition function P: Difference between revisions

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 Took 131ms</pre>
+=={{header|Elixir}}==
+Loosely based on the Erlang version.
+<lang Elixir>
+use Bitwise, skip_operators: true
+defmodule Partition do
+   def init(), do:
+      :ets.new :pN, [:set, :named_table, :private]
+   def gpentagonals(), do: Stream.unfold {1, 0}, &next/1
+   defp next({m, n}) do
+      a = case rem m, 2 do
+-> div m, 2
+-> m
+          end
+      {n, {m + 1, n + a}}
+   end
+   def p(0), do: 1
+   def p(n) do
+      case :ets.lookup :pN, n do
+         [{^n, val}] -> val
+         [] ->
+            {val, _} = gpentagonals()
+                       |> Stream.drop(1)
+                       |> Stream.take_while(fn m -> m <= n end)
+                       |> Stream.map(fn g -> p(n - g) end)
+                       |> Enum.reduce({0, 0},
+                              fn n, {a, sgn} -> {
+                                          a + (if sgn < 2, do: n, else: -n),
+                                          band(sgn + 1, 3)
+                                          }
+                              end)
+            :ets.insert :pN, {n, val}
+            val
+      end
+   end
+end
+Partition.init
+IO.puts Partition.p 6666
+</lang>
+{{Out}}
+<pre>
+193655306161707661080005073394486091998480950338405932486880600467114423441282418165863
+</pre>
 =={{header|Erlang}}==
 <lang Erlang>
@@ Line 295: / Line 341: @@
 sys	0m0.080s
 </pre>
 =={{header|F_Sharp|F#}}==
 An implementation of the formula in the task description. P(123456) is included for comparison with the largest value in the related task.