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9. Flex Predicates 124<br />
<strong>flex</strong> toolkit<br />
threshold value.<br />
crss(+Names,-Name,+FiringMechanism,-If,-Then,-Vars)<br />
FiringMechanism is one of {repeat,first,last,all} using first will give the same<br />
behaviour as crss/3 .<br />
crss( +Names,-Name,+FiringMechanism,-If,-Then,-Vars,+Threshold )<br />
Threshold is a value for chosing the rule or rules with the best score.<br />
cycle( +Name,+Names,-Newnames )<br />
This is a built-in program for re-organising the rule agenda after each cycle<br />
of the forward chaining engine according to cyclic rotation. It is defined by<br />
the program:<br />
cycle( Name, Names, Newnames ) :-<br />
append( Front, [Name|OldBack], Names ),<br />
append( Front, [Name], NewBack ),<br />
append( OldBack, NewBack, Newnames ).<br />
dereference( +Term,-Value )<br />
This is the kernel of the <strong>flex</strong> run-time procedures. It is used throughout the<br />
system as a means of interpreting <strong>flex</strong> objects. See the earlier chapter<br />
'Interpretation of KSL', for a complete description of the dereferencing<br />
mechanism.<br />
descendant( +Frame,-Descendant )<br />
Descendant is a descendant of Frame in the hierarchy. That is,<br />
Descendant is the Frame itself, or a child frame, or a grandchild frame, or<br />
a great-grandchild frame, etc.<br />
Example<br />
?- descendant( animal, D ).<br />
D = animal<br />
D = mammal<br />
D = whale<br />
D = moby_dick<br />
disable_rules( +Names )<br />
All the rules in the list Names are disabled, and will not be considered for<br />
firing. It is as if they have been temporarily removed from the workspace.<br />
Example<br />
disable_rules( [prescribe_lomotil,fill_B_from_A] ) .
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