ntics</TH></TR>
    <TR>
        <TD VALIGN="top">convertible to <A HREF="../guide/traits.html#category_tags"><CODE>optimally_buffered_tag</CODE></A></TD>
        <TD>Returns <CODE>t.optimal_buffer_size()</CODE>.</TD>
    </TR>
    <TR>
        <TD VALIGN="top">convertible to <A HREF="../guide/traits.html#category_tags"><CODE>filter_tag</CODE></A> but not to <A HREF="../guide/traits.html#category_tags"><CODE>optimally_buffered_tag</CODE></A></TD>
        <TD>Returns <A HREF='../macros/buffer_sizes.html'><CO