write_xyz Subroutine

subroutine write_xyz(self, unit, comment_line)
   class(structure_type), intent(in) :: self
   integer, intent(in) :: unit
   character(len=*), intent(in), optional :: comment_line
   integer :: iat
   logical :: expo

   write(unit, '(i0)') self%nat
   if (present(comment_line)) then
      write(unit, '(a)') comment_line
   else
      if (allocated(self%comment)) then
         write(unit, '(a)') self%comment
      else
         write(unit, '(a)')
      end if
   end if
   expo = maxval(self%xyz) > 1.0e+5 .or. minval(self%xyz) < -1.0e+5
   if (expo) then
      do iat = 1, self%nat
         write(unit, '(a4, 1x, 3es24.14)') &
            & self%sym(self%id(iat)), self%xyz(:, iat)*autoaa
      enddo
   else
      do iat = 1, self%nat
         write(unit, '(a4, 1x, 3f24.14)') &
            & self%sym(self%id(iat)), self%xyz(:, iat)*autoaa
      enddo
   end if

end subroutine write_xyz