subroutine opt_out (in_file, out_file, vari, value)

  use bmad

  use constraints_mod
  implicit none

  type (indep_var_struct)  vari

  real*8 value(*)

  integer i, j, n, ix, i_sc, ix_sc, ip, ip_tot, ix_in, ix_out
  integer iu0, iu1, iu2, ix_ex, ix1, ix2
  integer ixv, ixe

  character*(*) in_file, out_file
!  character*132 line, line_in, line_out, string
  character*200 line, line_in, line_out, string
  character*40 ele_name
  character*16 val_name

  logical :: init_needed = .true., var_located(1000)
  logical need_another_line, check_vars, unlocated_exist

  logical :: first_time_through = .true.

  type ptr_struct
     integer n_line, n_command, n_var
     logical overlay
  end type ptr_struct

  type (ptr_struct)  ptr(0:1000)

  save iu0, iu1, ptr, ip_tot, unlocated_exist, var_located

! parser file

  if (init_needed) then
     iu0 = lunget()
     open (unit = iu0, file = in_file, status = 'old', action='read')
     iu1 = lunget()
     open (unit = iu1, status = 'scratch')

     ip = 0                         ! number of variables located
     n = 0                          ! line number count
     ptr(0)%n_line = 0
     ptr(0)%n_command = 0
     need_another_line = .true.
     do j = 1, vari%n_var
        var_located(j) = .false.          ! not yet
     enddo

     do while (.true.)
        if (need_another_line) then
100        read (iu0, '(a)', end = 1000) line
           write (iu1, '(a)') line
           n = n + 1                            ! line number
           ix = index(line, '!')
           if (ix == 1) goto 100              ! read again if a comment line
           if (ix > 1) line = line(:ix-1)    ! strip off comment
           i_sc = 1                             ! command count on this line
        else
           line = line(ix_sc+1:)                ! strip off old command
           i_sc = i_sc + 1                      ! next command on this line
        endif
        
        ix_sc = index(line, ';')
        if (ix_sc == 0) then
           need_another_line = .true.
           string = line
        else
           need_another_line = .false.
           string = line(:ix_sc)
        endif

        check_vars = .false.
        call str_upcase (string, string)
        ix1 = index(string, '[')
        
        if (ix1 /= 0) then
           ix2 = index(string, ']')
           call string_trim (string(:ix1-1), ele_name, ix)
           val_name = string(ix1+1:ix2-1)
           ptr(ip+1)%overlay = .false.
           check_vars = .true.
        elseif (index(string, 'OVERLAY') /= 0) then   ! overlay ?
           ix1 = index(string, ':')
           call string_trim (string(:ix1-1), ele_name, ix)
           do
              ix1 = index(string, '}')
              if (ix1 /= 0) exit
              if (index(string, '&') == 0) then
                 print *, 'ERROR IN OPT_OUT: CANNOT FIND "}" OR "&" FOR AN OVERLAY!'
                 call err_exit
              endif
              read (iu0, '(a)', end = 1000) string
              !          write (iu1, '(a)') line
              write (iu1, '(a)') string
              n = n + 1
           enddo
           string = string(ix1:)
           ix1 = index(string, ',')
           string = string(ix1+1:)
           ix2 = index(string, '=')
           call string_trim(string(:ix2-1), val_name, ix)
           ptr(ip+1)%overlay = .true.
           check_vars = .true.
        endif

        if (check_vars) then
           do j = 1, vari%n_var
              if (vari%v(j)%ele_name == ele_name .and.  &
                   vari%v(j)%val_name == val_name) then
                 ip = ip + 1
                 ptr(ip)%n_line = n
                 ptr(ip)%n_command = i_sc
                 ptr(ip)%n_var = j
                 var_located(j) = .true.
                 goto 500
              endif
           enddo
500        continue
        endif
        
     enddo

1000 continue
     ip_tot = ip
     close (unit = iu0)

     unlocated_exist = .false.
     do i = 1, vari%n_var
        if (.not. var_located(i)) unlocated_exist = .true.
     enddo

     init_needed = .false.

  endif

  ! write the results to a new file

  rewind (unit = iu1)
  iu2 = lunget()
  if(first_time_through)then
     open (unit = iu2, file = out_file)
     first_time_through = .false.
  else
     open (unit = iu2, file = out_file, status = 'old')
  endif
  
  do ip = 1, ip_tot

     do i = ptr(ip-1)%n_line+1, ptr(ip)%n_line-1
        read (iu1, '(a)') line
        write (iu2, '(a)') trim(line)
     enddo
     
     if (ptr(ip)%n_line > ptr(ip-1)%n_line) then
        read (iu1, '(a)') line_in
        i_sc = ptr(ip)%n_command
        ix_in = 1
        ix_out = 1
     else
        i_sc = ptr(ip)%n_command - ptr(ip-1)%n_command
     endif
     
     do i = 1, i_sc-1
        ix_sc = index (line_in(ix_in:), ';')
        line_out(ix_out:) = line_in(ix_in:ix_in+ix_sc-1)
        ix_in = ix_in + ix_sc
        ix_out = ix_out + ix_sc
     enddo

     if (ptr(ip)%overlay) then
        ix1 = index (line_in(ix_in:), '}')
        ix2 = index (line_in(ix_in+ix1:), '=')
        !      ix = ix1 + ix2 - 1
        ix = ix1 + ix2
     else
        ix = index(line_in(ix_in:), ':=') + 1           ! old style
        if (ix == 1) ix = index(line_in(ix_in:), '=')   ! new style
     endif

     if (ix <= 0) then
        print *, 'ERROR IN OPT_OUT: Could not process this line: '
        print *, line
        call err_exit
     endif

     line_out(ix_out:) = line_in(ix_in:ix_in+ix)

     ix_in = ix_in + ix
     ix_out = ix_out + ix
     !    ix_out = ix_out + ix + 1
     !    ix_in = ix_in + ix + 1
     
     j = ptr(ip)%n_var
     write (line_out(ix_out:), '(es22.10)') value(j)
     ix_out = ix_out + 23
     !    ix_out = ix_out + 14
     
     ix_ex = index(line_in(ix_in:), '!')
     ix_sc = index(line_in(ix_in:), ';')

     if (ix_ex /= 0 .or. ix_sc /= 0) then
        if (ix_ex /= 0 .and. ix_sc /= 0) then
           ix = min(ix_ex, ix_sc)
        else
           ix = max(ix_ex, ix_sc)
        endif
        line_out(ix_out:) = line_in(ix_in+ix-1:)
        ix_in = ix_in + ix
        ix_out = ix_out + ix
     endif

     if (ptr(ip+1)%n_line /= ptr(ip)%n_line) then
        write (iu2, '(a)') trim(line_out)
     endif
     
  enddo

  do while (.true.)
     read (iu1, '(a)', end = 2000) line
     write (iu2, '(a)') trim(line)
  enddo
2000 continue

!

  if (unlocated_exist) then
     
     write (iu2, *)
     write (iu2, *) '! Vars not in original file'
     write (iu2, *)

     do j = 1, vari%n_var
        if (.not. var_located(j)) then
           write (iu2, '(4a, g20.8)') trim(vari%v(j)%ele_name), '[',  &
                trim(vari%v(j)%val_name), '] =', value(j)
        endif
     enddo
     
  endif

!

  close(iu2)

end subroutine opt_out