f_no               36 old_code/2015linfty/iodof.h   size_t f_no;
f_no               48 old_code/2015linfty/iodof.h   : filename {filename_series_prefix}, io_dir {write_or_read}, f_no {starting_no}
f_no               68 old_code/2015linfty/iodof.h   const std::string curr_file {filename + std::to_string(f_no)};