<primary>bit_length</primary>
        </indexterm>
        <function>bit_length</function> ( <type>bit</type> )
        <returnvalue>integer</returnvalue>
       </para>
       <para>
        Returns number of bits in the bit string.
       </para>
       <para>
        <literal>bit_length(B'10111')</literal>
        <returnvalue>5</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>length</primary>
        </indexterm>
        <indexterm>
         <primary>bit string</primary>
         <secondary>length</secondary>
        </indexterm>
        <function>length</function> ( <type>bit</type> )
        <returnvalue>integer</returnvalue>
       </para>
       <para>
        Returns number of bits in the bit string.
       </para>
       <para>
        <literal>length(B'10111')</literal>
        <returnvalue>5</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>octet_length</primary>
        </indexterm>
        <function>octet_length</function> ( <type>bit</type> )
        <returnvalue>integer</returnvalue>
       </para>
       <para>
        Returns number of bytes in the bit string.
       </para>
       <para>
        <literal>octet_length(B'1011111011')</literal>
        <returnvalue>2</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>overlay</primary>
        </indexterm>
        <function>overlay</function> ( <parameter>bits</parameter> <type>bit</type> <literal>PLACING</literal> <parameter>newsubstring</parameter> <type>bit</type> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
        <returnvalue>bit</returnvalue>
       </para>
       <para>
        Replaces the substring of <parameter>bits</parameter> that starts at
        the <parameter>start</parameter>'th bit and extends
        for <parameter>count</parameter> bits
        with <parameter>newsubstring</parameter>.
        If <parameter>count</parameter> is omitted, it defaults to the length
        of <parameter>newsubstring</parameter>.
       </para>
       <para>
        <literal>overlay(B'01010101010101010' placing B'11111' from 2 for 3)</literal>
        <returnvalue>0111110101010101010</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>position</primary>
        </indexterm>
        <function>position</function> ( <parameter>substring</parameter> <type>bit</type> <literal>IN</literal> <parameter>bits</parameter> <type>bit</type> )
        <returnvalue>integer</returnvalue>
       </para>
       <para>
        Returns first starting index of the specified <parameter>substring</parameter>
        within <parameter>bits</parameter>, or zero if it's not present.
       </para>
       <para>
        <literal>position(B'010' in B'000001101011')</literal>
        <returnvalue>8</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>substring</primary>
        </indexterm>
        <function>substring</function> ( <parameter>bits</parameter> <type>bit</type> <optional> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> </optional> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
        <returnvalue>bit</returnvalue>
       </para>
       <para>
        Extracts the substring of <parameter>bits</parameter> starting at
        the <parameter>start</parameter>'th bit if that is specified,
        and stopping