(including SQL and PL/pgSQL)
       let you use the name in the function body.  For other languages the
       name of an input argument is just extra documentation, so far as
       the function itself is concerned; but you can use input argument names
       when calling a function to improve readability (see <xref
       linkend="sql-syntax-calling-funcs"/>).  In any case, the name
       of an output argument is significant, because it defines the column
       name in the result row type.  (If you omit the name for an output
       argument, the system will choose a default column name.)
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><replaceable class="parameter">argtype</replaceable></term>

     <listitem>
      <para>
       The data type(s) of the function's arguments (optionally
       schema-qualified), if any. The argument types can be base, composite,
       or domain types, or can reference the type of a table column.
      </para>
      <para>
       Depending on the implementation language it might also be allowed
       to specify <quote>pseudo-types</quote> such as <type>cstring</type>.
       Pseudo-types indicate that the actual argument type is either
       incompletely specified, or outside the set of ordinary SQL data types.
      </para>
      <para>
       The type of a column is referenced by writing
       <literal><replaceable
       class="parameter">table_name</replaceable>.<replaceable
       class="parameter">column_name</replaceable>%TYPE</literal>.
       Using this feature can sometimes help make a function independent of
       changes to the definition of a table.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><replaceable class="parameter">default_expr</replaceable></term>

     <listitem>
      <para>
       An expression to be used as default value if the parameter is
       not specified.  The expression has to be coercible to the
       argument type of the parameter.
       Only input (including <literal>INOUT</literal>) parameters can have a default
        value.  All input parameters following a
       parameter with a default value must have default values as well.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><replaceable class="parameter">rettype</replaceable></term>

     <listitem>
      <para>
       The return data type (optionally schema-qualified). The return type
       can be a base, composite, or domain type,
       or can reference the type of a table column.
       Depending on the implementation language it might also be allowed
       to specify <quote>pseudo-types</quote> such as <type>cstring</type>.
       If the function is not supposed to return a value, specify
       <type>void</type> as the return type.
      </para>
      <para>
       When there are <literal>OUT</literal> or <literal>INOUT</literal> parameters,
       the <literal>RETURNS</literal> clause can be omitted.  If present, it
       must agree with the result type implied by the output parameters:
       <literal>RECORD</literal> if there are multiple output parameters, or
       the same type as the single output parameter.
      </para>
      <para>
       The <literal>SETOF</literal>
       modifier indicates that the function will return a set of
       items, rather than a single item.
      </para>
      <para>
       The type of a column is referenced by writing
       <literal><replaceable
       class="parameter">table_name</replaceable>.<replaceable
       class="parameter">column_name</replaceable>%TYPE</literal>.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><replaceable class="parameter">column_name</replaceable></term>

     <listitem>
      <para>
       The name of an output column in the <literal>RETURNS TABLE</literal>
       syntax.  This is effectively another way of declaring a named
       <literal>OUT</literal> parameter, except that