[Xsb-commits] CVS: XSB/docs/userman hooks.tex,1.5,1.6

[David S. W. <dw...@us...>]

Update of /cvsroot/xsb/XSB/docs/userman
In directory usw-pr-cvs1:/tmp/cvs-serv29550

Modified Files:
	hooks.tex 
Log Message:
Added example of how to use hooks to give a global "fail-if-undefined" 
operation.


Index: hooks.tex
===================================================================
RCS file: /cvsroot/xsb/XSB/docs/userman/hooks.tex,v
retrieving revision 1.5
retrieving revision 1.6
diff -u -r1.5 -r1.6
--- hooks.tex	17 Dec 2001 22:37:45 -0000	1.5
+++ hooks.tex	15 Jul 2002 12:27:42 -0000	1.6
@@ -8,6 +8,19 @@
 events. All the predicates described below must be imported from {\tt
 xsb\_hook}.
 
+An example of the use of hooks is to have XSB fail quietly when it
+encounters an undefined predicate.  This can be achieved by the
+the example code, which is explained in the following sections.
+
+\begin{verbatim}
+:- import add_xsb_hook/1,xsb_undefined_predicate_hook/1 from xsb_hook.
+
+:- add_xsb_hook(xsb_undefined_predicate_hook(undef_fail(_))).
+
+undef_fail(_).
+\end{verbatim}
+
+
 \section{Adding and Removing Hooks}
 
 A hook in XSB can be either a 0-ary predicate or a unary predicate.