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|Hooks for integrating libraries
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 section A.23 for editing hooks and section 4.11 for hooking into the message system.
user to list the currently
called predicate. This hook may be defined to list only relevant clauses
of the indicated Goal and/or show the actual source code in
an editor. See also portray/1
?- help(picture). is caught by the XPCE help hook
to give help on the class picture. Defined actions are: