df_info Subroutine

    subroutine df_info(df, unit)
        type(data_frame), intent(in) :: df
        integer, intent(in), optional :: unit

        integer :: out_unit, i, dtype
        character(len=20) :: type_name
        integer, dimension(2) :: dims

        if (present(unit)) then
            out_unit = unit
        else
            out_unit = 6  ! stdout
        end if

        dims = df_shape(df)

        write (out_unit, '(a)') repeat('=', 60)
        write (out_unit, '(a)') 'DataFrame Information'
        write (out_unit, '(a)') repeat('=', 60)
        write (out_unit, '(a,i0,a,i0,a)') 'Shape: (', dims(1), ' rows, ', dims(2), ' columns)'
        write (out_unit, '(a,l1)') 'Has headers: ', df % get_with_headers()

        if (df % ncols() > 0) then
            write (out_unit, '(a)') ''
            write (out_unit, '(a)') 'Columns:'
            write (out_unit, '(a)') repeat('-', 60)

            do i = 1, df % ncols()
                dtype = df % dtype(i)

                select case (dtype)
                case (REAL_NUM)
                    type_name = 'real'
                case (INTEGER_NUM)
                    type_name = 'integer'
                case (LOGICAL_NUM)
                    type_name = 'logical'
                case (CHARACTER_NUM)
                    type_name = 'character'
                case (COMPLEX_NUM)
                    type_name = 'complex'
                case default
                    type_name = 'unknown'
                end select

                if (df % get_with_headers()) then
                    write (out_unit, '(i4,2a,t30,3a)') i, '. ', trim(df % header(i)), &
                        '(', trim(type_name), ')'
                else
                    write (out_unit, '(i4,2a,a)') i, '. Column (', trim(type_name), ')'
                end if
            end do
        end if

        write (out_unit, '(a)') repeat('=', 60)
    end subroutine df_info