life/001/src/life.erl

   1 -module(life).
   2 -behaviour(application).
   3
   4
   5 %% API
   6 -export([bang/0]).
   7
   8 %% Callbacks
   9 -export([start/2, stop/1]).
  10
  11
  12 -define(DIRECTIONS, ['N', 'NE', 'E', 'SE', 'S', 'SW', 'W', 'NW']).
  13
  14
  15 %% ============================================================================
  16 %% API
  17 %% ============================================================================
  18
  19 bang() ->
  20     application:start(?MODULE).
  21
  22
  23 %% ============================================================================
  24 %% Callbacks
  25 %% ============================================================================
  26
  27 start(_StartType, _StartArgs) ->
  28     {ok, X} = application:get_env(?MODULE, x),
  29     {ok, Y} = application:get_env(?MODULE, y),
  30     CellData = cell_data(X, Y),
  31     life_god:start_link(X, Y, CellData).
  32
  33
  34 stop(_State) ->
  35     ok.
  36
  37
  38 %% ============================================================================
  39 %% Internal
  40 %% ============================================================================
  41
  42 cell_data(X, Y) ->
  43     N = X * Y,
  44     [cell_datum(X, N, ID) || ID <- lists:seq(1, N)].
  45
  46
  47 cell_datum(X, N, ID) ->
  48     Name = integer_to_atom(ID),
  49     NeighborNames = filter_offsides(N,
  50         [integer_to_atom(neighbor_id(Dir, X, ID)) || Dir <- ?DIRECTIONS]
  51     ),
  52     {ID, Name, NeighborNames}.
  53
  54
  55 neighbor_id(Direction, X, ID) -> ID + offset(Direction, X).
  56
  57
  58 offset('N' , X) -> ensure_negative(X);
  59 offset('NE', X) -> ensure_negative(X - 1);
  60 offset('E' , _) ->                     1;
  61 offset('SE', X) ->                 X + 1;
  62 offset('S' , X) ->                 X;
  63 offset('SW', X) ->                 X - 1;
  64 offset('W' , _) -> ensure_negative(    1);
  65 offset('NW', X) -> ensure_negative(X + 1).
  66
  67
  68 ensure_negative(N) when N < 0 -> N;
  69 ensure_negative(N) -> -(N).
  70
  71
  72 filter_offsides(N, IDs) ->
  73     [ID || ID <- IDs, is_onside(N, atom_to_integer(ID))].
  74
  75
  76 is_onside(_, ID) when ID < 1 -> false;
  77 is_onside(N, ID) when ID > N -> false;
  78 is_onside(_, _) -> true.
  79
  80
  81 atom_to_integer(Atom) ->
  82     list_to_integer(atom_to_list(Atom)).
  83
  84
  85 integer_to_atom(Integer) ->
  86     list_to_atom(integer_to_list(Integer)).