anchor.diff:    %% valid so return atom
     julian;
   %% add other valid fractal algorithms here as they are created
  -check_fractal_alg(FractalAlg) ->
  +check_fractal_alg(_FractalAlg) ->
     erlang:error(this_fractal_algorithm_not_implemented).
   
   %% get and validate image file name
  
positive.code: 
  jason2atom(BinaryMap) ->
    Width  = maps:get(<<"width">>, BinaryMap),
  
    Height = get_height(BinaryMap),
    FractalAlg = get_fractal_alg(BinaryMap),
    ImageFile = get_image_file(BinaryMap),
    
    ColorAlg = maps:get(<<"colorAlg">>, BinaryMap),
    CReal = maps:get(<<"cReal">>, BinaryMap),
    CImaginary = maps:get(<<"cImaginary">>, BinaryMap),
    ZReal = maps:get(<<"zReal">>, BinaryMap),
  
negative.code:   check_illegal_filename_chars(ImageFile),
    %% all good so return string
    ImageFile;
  check_image_file(_ImageFile) ->
    erlang:error(imageFile_is_not_binary_nor_list).
  
  check_illegal_filename_chars( [] ) ->
  