for(; (line_end!=source_end && *line_end!='\n'); ++line_end) ;
SetForScope<string::const_iterator> stop_at_line_end(source_end, line_end);
for(; (line_end!=source_end && *line_end!='\n'); ++line_end) ;
SetForScope<string::const_iterator> stop_at_line_end(source_end, line_end);