anchor.diff:    use arguments, only: read_opt, read_opt_arg
     use parser, only: parser_nfields,remove_comments, parse_next_line
     implicit none
  -  
  +
     character(len=string_size) :: data_type
     integer                    :: nvars=0, nclasses=0
     integer,       allocatable :: seqs(:,:)
  
positive.code: ! Copyright (C) 2015-2017, Simone Marsili 
  ! All rights reserved.
  ! License: BSD 3 clause
  
  
negative.code:         iarg = iarg + 1
          call read_opt_arg(iarg,nargs,n_digits,err)
          if (err == 2) then
             write(0,*) 'ERROR ! option "-d": missing argument'
             stop
          end if
       case default
          write(0,*) 'ERROR ! unkown argument '//trim(arg)
          write(0,100)
          stop
       end select
    end do args_loop
  