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One-Dimensional Cellular Automaton in Elixir
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| *.beam |
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| defmodule CellularAutomata do | |
| @initial [0, 1, 0] | |
| def run(generations, rule_number) do | |
| rule_fn = rule(rule_number) | |
| width = generations * 2 + 1 | |
| Stream.iterate(@initial, &(step(&1, rule_fn))) | |
| |> Enum.take(generations) | |
| |> Enum.map(&(center_pad(&1, width, 0))) | |
| |> Enum.each(&print/1) | |
| end | |
| # Generate a rule function | |
| def rule(n) do | |
| digits = to_binary(n, 8) | |
| rules = Enum.to_list(7..0) | |
| |> Enum.map(&(to_binary(&1, 3))) | |
| map = Enum.zip(rules, digits) | |
| |> Map.new | |
| fn ns -> map[ns] end | |
| end | |
| # Advance the cellular automata one generation. | |
| # | |
| # The edges will be padded with zeroes to account for the boundary conditions. | |
| defp step(field, rule) do | |
| Enum.chunk([0, 0] ++ field ++ [0, 0], 3, 1) |> Enum.map(rule) | |
| end | |
| # Convert an integer into a list of binary digits, left-padded with zeroes. | |
| defp to_binary(n, size), do: Integer.digits(n, 2) |> left_pad(size, 0) | |
| defp left_pad(list, n, value) when length(list) < n do | |
| left_pad([value | list], n, value) | |
| end | |
| defp left_pad(list, _, _), do: list | |
| # This is gross. | |
| defp center_pad(list, width, value) when length(list) < width do | |
| center_pad([value|list] ++ [value], width, value) | |
| end | |
| defp center_pad(list, _, _), do: list | |
| defp print([0|tail]) do | |
| IO.write(" ") | |
| print(tail) | |
| end | |
| defp print([1|tail]) do | |
| IO.write("X") | |
| print(tail) | |
| end | |
| defp print([]), do: IO.puts("") | |
| end |
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