anchor.diff:                  end;
               _ ->
                   if
  -                    % For options with short form and argument.
  +                    %% For options with short form and argument.
                       Short =/= undefined ->
                           [$\s, $[, $-, Short, $\s, $<, atom_to_list(Name), $>, $]];
  -                    % For options with only long form and argument.
  +                    %% For options with only long form and argument.
                       Long =/= undefined ->
                           [$\s, $[, $-, $-, Long, $\s, $<, atom_to_list(Name), $>, $]];
  -                    % For options with neither short nor long form and argument.
  +                    %% For options with neither short nor long form and argument.
                       true ->
                           [$\s, $<, atom_to_list(Name), $>]
                   end
  
positive.code:                     parse(OptSpecList, [Name | OptAcc], ArgAcc, ArgPos, Args);
  
                  {_Name, _Short, Long, _ArgSpec, _Help} = OptSpec ->
                      % The option argument string is empty, but the option requires
                      % an argument, so we look into the next string in the list.
                      parse_option_next_arg(OptSpecList, OptAcc, ArgAcc, ArgPos, Args, OptSpec);
                  false ->
                      throw({error, {invalid_option, OptStr}})
              end
  
negative.code: is_valid_arg(boolean, Arg) ->
      is_boolean_arg(Arg);
  is_valid_arg(integer, Arg) ->
      is_non_neg_integer_arg(Arg);
  is_valid_arg(float, Arg) ->
      is_non_neg_float_arg(Arg);
  is_valid_arg(_Type, _Arg) ->
      true.
  
  
  -spec is_implicit_arg(arg_spec(), nonempty_string()) -> boolean().
  is_implicit_arg({Type, _DefaultArg}, Arg) ->
      is_implicit_arg(Type, Arg);
  is_implicit_arg(boolean, Arg) ->
      not is_boolean_arg(Arg);
  is_implicit_arg(integer, Arg) ->
      not is_integer_arg(Arg);
  is_implicit_arg(_Type, _Arg) ->
      false.
  
  
  -spec is_boolean_arg(string()) -> boolean().
  