flex Expert System Toolkit - LPIS

9. Flex Predicates 148
the agenda. It is defined by the program:
once( Name, [Name|Names], Names ).
once( Name, [Head|Names], [Head|Newnames]) :-
once( Name, Names, Newnames ).
possibles(+Name,+Names,-Newnames)
prove( +Goal )
This is a built-in program for re-organising the rule agenda after each cycle
of the forward chaining engine. It removes unsatisfied rules from the
agenda, and is defined by the program:
possibles( Name, Names, [Name|Newnames] ) :-
append( _, [Name|NewNames], Names ).
Dereference each of the arguments of the Goal and then try to prove it.
If there is a Prolog program for the Goal, then that program is run,
otherwise the workspace is searched for a matching fact (see new_fact/1),
and in addition a check is made that there are no matching exceptions (see
new_exception/1).
Example
?- prove( likes( X, @(father,peter)) )
X = mary
?- prove( likes( mary, fred) ).
no
where fred is not the father of peter.
reconsult_rules( +FileName )
Reconsult a flex ksl file.
remember_exception( +Term )
Add the given Term as a new exception in the workspace, which can be
accessed through the prove/1 and disprove/1 procedures.
If subsequent backtracking happens, then the asserted exception will be
removed.
Example
remember_exception( likes(mary,fred) ) .
remember_fact( +Term )
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