delete_input_list Subroutine

  subroutine delete_input_list(list)
    type(input_list),optional :: list
    type(input_node),pointer  :: p,c
    integer :: i
    if(present(list))then
       do
          p => list%root
          c => p%next
          if(.not.associated(c))exit  !empty list
          p%next => c%next !
          c%next=>null()
          do i=1,size(c%var)
             nullify(c%var(i)%i)
             nullify(c%var(i)%d)
             nullify(c%var(i)%l)
             nullify(c%var(i)%ch)
          enddo
          deallocate(c%var)
          deallocate(c)
       end do
       list%status=.false.
       deallocate(list%root)
    else
       do
          p => default_list%root
          c => p%next
          if(.not.associated(c))exit  !empty list
          p%next => c%next !
          c%next=>null()
          do i=1,size(c%var)
             nullify(c%var(i)%i)
             nullify(c%var(i)%d)
             nullify(c%var(i)%l)
             nullify(c%var(i)%ch)
          enddo
          deallocate(c%var)
          deallocate(c)
       end do
       default_list%status=.false.
       deallocate(default_list%root)
    endif
    p => null()
    c => null()
  end subroutine delete_input_list