Help with release note items

I need help understanding the following two release note items (see XXX):
    <listitem>     <para>      Create a general mechanism that supports casts to and from the      standard string
types(<type>TEXT</type>, <type>VARCHAR</type>,      <type>CHAR</type>) for <emphasis>every</emphasis> datatype, by
invokingthe datatype's I/O functions (Tom)  XXX examples?     </para>
 
     <para>      These new casts are assignment-only in the to-string direction,      explicit-only in the other
direction,and therefore should create no      surprising behavior.  Various      datatype-specific casting functions
thatwere equivalent to this      behavior were removed.     </para>    </listitem>
 
    <listitem>     <para>      Allow limited hashing when using two different data types (Tom)     </para>
     <para>      This allows hash joins, hash indexes, hashed subplans, and hash      aggregation to be used in
situationsinvolving cross-data-type      comparisons, if the data types have compatible hash functions.      Currently,
cross-data-typehashing support exists for      <type>smallint</type>/<type>integer</type>/<type>bigint</type>,      and
for<type>float4</type>/<type>float8</type>.  XXX how do you do      hash aggregate with two different data types
</para>   </listitem>
 


--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://postgres.enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +