namespace app
{
  outcome<void> go()  // NOT noexcept, this can throw STL exceptions e.g. bad_alloc
  {
    // Note that explicit construction is required when converting between differing types
    // of outcome and result. This makes it explicit what you intend to do as conversion
    // may be a lot more expensive than moves.

    // Try to GET this URL. If an unsuccessful HTTP status is returned, serialise a string
    // containing a description of the HTTP status code and the URL which failed, storing
    // that into a httplib_error exception type which is stored as an exception ptr. The
    // TRY operation below will return that exception ptr to be rethrown in the caller.
    // Otherwise the fetched data is returned in a std::string data.
    BOOST_OUTCOME_TRY(data, (outcome<std::string>(httplib::get("http://www.nedproductions.biz/"))));
    string_view data_view(data);

    // HTML tidy the fetched data. If the C library fails due to an error corresponding to
    // a standard library exception type, throw that. Otherwise, synthesise an exception
    // ptr of type tidylib_error which stores the error code returned in an error code with
    // generic category (i.e. errno domain).
    // TRY operation below will return that exception ptr to be rethrown in the caller.
    // Otherwise the tidied data is returned into holdmem, with the string view updated to
    // point at the tidied data.
    BOOST_OUTCOME_TRY(holdmem, (tidy_html(data_view)));

    // Write the tidied data to some file. If the write fails, synthesise a filesystem_error
    // exception ptr exactly as if one called filelib::write_file(data_view).value().
    BOOST_OUTCOME_TRY(written, (outcome<size_t>(filelib::write_file(data_view))));
    return success();
  }
}