anchor.diff:  % @author Marc Worrell
  -%% @copyright 2014 Marc Worrell
  +%% @copyright 2014-2021 Marc Worrell
   %% @doc Fetch (part of) the data of an Url, including its headers.
   
  -%% Copyright 2014 Marc Worrell
  +%% Copyright 2014-2021 Marc Worrell
   %%
   %% Licensed under the Apache License, Version 2.0 (the "License");
   %% you may not use this file except in compliance with the License.
  
positive.code:     case normalize_url(Url0) of
          {ok, {Host, UrlBin}} ->
              Url = to_list(UrlBin),
              Headers = [
                  {"Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"},
                  {"Accept-Encoding", "identity"},
                  {"Accept-Charset", "UTF-8;q=1.0, ISO-8859-1;q=0.5, *;q=0"},
                  {"Accept-Language", "en,*;q=0"},
                  {"User-Agent", httpc_ua(Url)}
              ] ++ case Max of
                  undefined -> [];
                  _ -> [ {"Range", "bytes=0-"++integer_to_list(Max-1)} ]
  
negative.code:                 | {timeout, pos_integer()}
                  | {max_length, pos_integer()}
                  | {authorization, binary() | string()}
                  | {accept, binary() | string()}
                  | {user_agent, binary() | string()}
                  | {language, atom()}
                  | insecure.
  
  -export_type([
  