/usr/lib/swi-prolog/doc/Manual/intlibs.html

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<h2 id="sec:intlibs"><a id="sec:B.8"><span class="sec-nr">B.8</span> <span class="sec-title">Hooks 
for integrating libraries</span></a></h2>

<a id="sec:intlibs"></a>

<p>Some libraries realise an entirely new programming paradigm on top of 
Prolog. An example is XPCE which adds an object system to Prolog as well 
as an extensive set of graphical primitives. SWI-Prolog provides several 
hooks to improve the integration of such libraries. See also
<a class="sec" href="listing.html">section 4.5</a> for editing hooks and <a class="sec" href="exception.html">section 
4.10.3</a> for hooking into the message system.

<dl class="latex">
<dt class="pubdef"><a id="prolog_list_goal/1"><strong>prolog_list_goal</strong>(<var>:Goal</var>)</a></dt>
<dd class="defbody">
Hook, normally not defined. This hook is called by the 'L' command of 
the tracer in the module <code>user</code> to list the currently called 
predicate. This hook may be defined to list only relevant clauses of the 
indicated <var>Goal</var> and/or show the actual source code in an 
editor. See also <a id="idx:portray1:1879"></a><a class="pred" href="termrw.html#portray/1">portray/1</a> 
and <a id="idx:multifile1:1880"></a><a class="pred" href="dynamic.html#multifile/1">multifile/1</a>.</dd>
<dt class="pubdef"><a id="prolog:debug_control_hook/1"><strong>prolog:debug_control_hook</strong>(<var>:Action</var>)</a></dt>
<dd class="defbody">
Hook for the debugger control predicates that allows the creator of more 
high-level programming languages to use the common front-end predicates 
to control the debugger. For example, XPCE uses these hooks to allow for 
spying methods rather than predicates. <var>Action</var> is one of:

<dl class="latex">
<dt><strong>spy</strong>(<var>Spec</var>)</dt>
<dd class="defbody">
Hook in <a id="idx:spy1:1881"></a><a class="pred" href="debugger.html#spy/1">spy/1</a>. 
If the hook succeeds <a id="idx:spy1:1882"></a><a class="pred" href="debugger.html#spy/1">spy/1</a> 
takes no further action.
</dd>
<dt><strong>nospy</strong>(<var>Spec</var>)</dt>
<dd class="defbody">
Hook in <a id="idx:nospy1:1883"></a><a class="pred" href="debugger.html#nospy/1">nospy/1</a>. 
If the hook succeeds <a id="idx:nospy1:1884"></a><a class="pred" href="debugger.html#nospy/1">nospy/1</a> 
takes no further action. If <a id="idx:spy1:1885"></a><a class="pred" href="debugger.html#spy/1">spy/1</a> 
is hooked, it is advised to place a complementary hook for
<a id="idx:nospy1:1886"></a><a class="pred" href="debugger.html#nospy/1">nospy/1</a>.
</dd>
<dt><strong>nospyall</strong></dt>
<dd class="defbody">
Hook in <a id="idx:nospyall0:1887"></a><a class="pred" href="debugger.html#nospyall/0">nospyall/0</a>. 
Should remove all spy points. This hook is called in a failure-driven 
loop.
</dd>
<dt><strong>debugging</strong></dt>
<dd class="defbody">
Hook in <a id="idx:debugging0:1888"></a><a class="pred" href="debugger.html#debugging/0">debugging/0</a>. 
It can be used in two ways. It can report the status of the additional 
debug points controlled by the above hooks and fail to let the system 
report the others, or it succeeds, overruling the entire behaviour of <a id="idx:debugging0:1889"></a><a class="pred" href="debugger.html#debugging/0">debugging/0</a>.
</dd>
</dl>

</dd>
<dt class="pubdef"><a id="prolog:help_hook/1"><strong>prolog:help_hook</strong>(<var>+Action</var>)</a></dt>
<dd class="defbody">
Hook into <a id="idx:help0:1890"></a><a class="pred" href="help.html#help/0">help/0</a> 
and <a id="idx:help1:1891"></a><a class="pred" href="help.html#help/1">help/1</a>. 
If the hook succeeds, the built-in actions are not executed. For 
example, <code>?- help(picture).</code> is caught by the XPCE help hook 
to give help on the class <em>picture</em>. Defined actions are:

<dl class="latex">
<dt><strong>help</strong></dt>
<dd class="defbody">
User entered plain <a id="idx:help0:1892"></a><a class="pred" href="help.html#help/0">help/0</a> 
to give default help. The default performs
<code>help(<a id="idx:help1:1893"></a><a class="pred" href="help.html#help/1">help/1</a>)</code>, 
giving help on help.
</dd>
<dt><strong>help</strong>(<var>What</var>)</dt>
<dd class="defbody">
Hook in <a id="idx:help1:1894"></a><a class="pred" href="help.html#help/1">help/1</a> 
on the topic <var>What</var>.
</dd>
<dt><strong>apropos</strong>(<var>What</var>)</dt>
<dd class="defbody">
Hook in <a id="idx:apropos1:1895"></a><a class="pred" href="help.html#apropos/1">apropos/1</a> 
on the topic <var>What</var>.
</dd>
</dl>

</dd>
</dl>

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swi-prolog-nox 6.6.4-2ubuntu1 / usr / lib / swi-prolog / doc / Manual / intlibs.html
