anchor.diff:  %%%%%%%%
   %% compute_fractal_data_file/1 API
   %%        ConfigMap    - config info
  -%%        creates file with list of rows (where each row is list of counts, 1 per pixel)
  -%%                     suitable to be read with file:consult
  +%%        creates file with list of rows
  +%%           (where each row is list of counts, 1 per pixel)
  +%%        suitable to be read with file:consult
   %%%%%%%%
   compute_fractal_data_file(ConfigMap) ->
       %% get config needed
  
positive.code:     compute_fractal_data( [],             % Rows starts empty
                          [],             % ThisRow starts empty
                          Width,          % XPix starts width and decrements to 1
                          XRealRight,     %% XR starts at right and decrements to by deltaX
                          DeltaX,
                          Width,          % width
                          Height,         % YPix starts height and decrements to 1
                          YImaginaryHigh, % YI starts at top and decrements by delta y
                          DeltaY,
                          Height,         % height
                          ConfigMap).    % map of parameters
  
negative.code:     NewRows = [ ThisRow | Rows ],
  
      % reset to begining of next row
      NewRowData = [],                               % reset data for row to empty
      NewXPix    = Width,                            % reset to end of line
      NewXR      = maps:get(xRealRight, ConfigMap),  % reset to end of line
      NewYPix    = YPix - 1,                         % increment row
      NewYI      = YI - DeltaY,                      % increment row
      compute_fractal_data( NewRows, NewRowData,
                     NewXPix, NewXR, DeltaX, Width,
                     NewYPix, NewYI, DeltaY, Height,
  