anchor.diff:  %% API
   -export([start/3, start/0]).
   
  -%% -define(DEBUG,true).
  +%% -define(debug, ok).
   
   -type dimension() :: pos_integer().
   -type onedir() :: -1 | 0 | 1.
  
positive.code:   io:format("Step ~p:~n",[Steps]),
    display(EndAnt, EndBoard, Width, Height),
    Time = timer:now_diff(T2,T1),
    io:format("Time elapsed: ~p s~n",[Time/1000000]).
  
  
  step(Board, _W, _H, Ant, MaxT, MaxT) -> {Board, Ant};
  
negative.code:   NewBoard = update_board(Board, W, H, APos, NewAPos),
  
  %%   io:format("new ant dir ~p~n",[NewADir]),
  
  %%   io:format("new ant pos ~p~n",[NewAPos]),
     if
       T > 30000 ->
        io:format("Step ~p:~n",[T+1]),
        display({NewAPos, NewADir}, NewBoard, W, H),
        timer:sleep(80)
       ;
       true -> ok
     end
    ,
  
    step(NewBoard, W, H, {NewAPos, NewADir}, T+1, MaxT).
  
  