anchor.diff:          case ArgSpec of
               undefined ->
                   if
  -                    % For options with short form and no argument.
  +                    %% For options with short form and no argument.
                       Short =/= undefined ->
                           [$\s, $[, $-, Short, $]];
  -                    % For options with only long form and no argument.
  +                    %% For options with only long form and no argument.
                       Long =/= undefined ->
                           [$\s, $[, $-, $-, Long, $]];
                       true ->
  
positive.code: is_valid_arg(boolean, Arg) ->
      is_boolean_arg(Arg);
  is_valid_arg(integer, Arg) ->
      is_integer_arg(Arg);
  is_valid_arg(float, Arg) ->
      is_float_arg(Arg);
  is_valid_arg(_Type, _Arg) ->
      true.
  
  
  -spec is_boolean_arg(string()) -> boolean().
  
negative.code:         case Long of
              undefined ->
                  case Short of
                      %% Neither short nor long form (non-option argument).
                      undefined ->
                          [$<, atom_to_list(Name), $>];
                      %% Only short form.
                      _ ->
                          [$-, Short]
                  end;
              _ ->
                  case Short of
                      %% Only long form.
                      undefined ->
                          [$-, $- | Long];
                      %% Both short and long form.
                      _ ->
                          [$-, Short, $,, $\s, $-, $- | Long]
                  end
  