anchor.diff:    implicit none
     private
     public :: command_line_read
  -  character(len=1), parameter                  :: nl=achar(10)
  -  character(len=long_string_size)              :: syntax = nl//& 
  -       '                                       elss-sample (v0.3.1)                                    '//nl//&
  -       '                                    ==========================                                 '//nl//&
  -       nl//&
  -       nl//&
  -       'Option                         Description                                     (Default Value)  '//nl//&
  -       '------------------------------------------------------------------------------------------------'//nl//&
  -       ' (-p|--prm) <path_to_file>     parameters file                                 (None)           '//nl//&   
  -       '        OR'//nl//&   
  -       ' (-c|--chk) <path_to_file>     checkpoint file                                 (None)           '//nl//&   
  -       nl//&
  -       nl//&
  -       ' (-h|--help)                   print this help message                         (None)           '//nl//&
  -       nl//&
  -       ' --prefix <strin               prefix for output files                         (None)           '//nl//&
  -       nl//&
  -       ' (-n|--nsweeps) <int>          num. of MC sweeps                               (1000)           '//nl//&
  -       nl//&
  -       ' (-u|--nupdate) <int>          stride (as num. of sweeps) for averages updates (10)             '//nl//&
  -       nl//&
  -       ' (-s|--seq) <path_to_file>     starting sequence file                          (None)           '//nl//&
  -       nl//&
  -       ' --seed <int>           init. the random seed (if 0, use system_clock)  (0)              '//nl//&
  -       '------------------------------------------------------------------------------------------------'//nl//&
  -       nl//&
  -       nl//&
  -       '------------------------------------------------------------------------------------------------'//nl//&
  -       ' For more information and usage examples, please check the project github repository:           '//nl//&
  -       ' https://github.com/simomarsili/elss                                                            '//nl//&
  -       '------------------------------------------------------------------------------------------------'//nl//&
  -       '                                                                                                    '
  +
   contains
   
     subroutine command_line_read(uprm,uchk,useq,rseed,beta,mc_nsweeps,nupdate,&
  
positive.code:        end if
      end if
  
    end subroutine command_line_read
  
  end module sample_command_line
  
negative.code: 
      if (nargs == 0) then
         ! no args: print syntax and stop
         write(0,100)
         error_code = 1
         return
      end if
  