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$Header: /cvsroot/pgsql/doc/src/sgml/xfunc.sgml,v 1.29 2001/01/20 20:59:29 petere Exp $

$Header: /cvsroot/pgsql/doc/src/sgml/xfunc.sgml,v 1.30 2001/01/22 16:11:17 tgl Exp $

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<chapter id="xfunc">

<function>PG_GETARG_<replaceable>xxx</replaceable>()</function>

macro that corresponds to the argument's datatype, and the result

is returned using a

<function>PG_GETARG_<replaceable>xxx</replaceable>()</function>

<function>PG_RETURN_<replaceable>xxx</replaceable>()</function>

macro for the return type.

</para>

<para>

Here we show the same functions as above, coded innew style:

Here we show the same functions as above, coded inversion-1 style:

<programlisting>

#include &lt;string.h&gt;

Datum

makepoint(PG_FUNCTION_ARGS)

{

/* Here, the pass-by-reference nature of Point is not hidden */

Point *pointx = PG_GETARG_POINT_P(0);

Point *pointy = PG_GETARG_POINT_P(1);

Point *new_point = (Point *) palloc(sizeof(Point));

<para>

The <command>CREATE FUNCTION</command> commands are the same as

for theold-style equivalents.

for theversion-0 equivalents.

</para>

<para>

test for NULL inputs to a non-strict function, return a NULL

result (from either strict or non-strict functions), return

<quote>set</quote> results, and implement trigger functions and

procedural-language call handlers. For more details see

procedural-language call handlers. Version-1 code is also more

portable than version-0, because it does not break ANSI C restrictions

on function call protocol. For more details see

<filename>src/backend/utils/fmgr/README</filename> in the source

distribution.

</para>