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    <p>Here's how you would typically do it with a simple comparison:</p> <pre><code>CLIPS&gt; (clear) CLIPS&gt; (deftemplate fact (slot name) (slot value)) CLIPS&gt; (deffacts test-data (fact (name data-1) (value 3)) (fact (name data-2) (value 1)) (fact (name data-3) (value 2)) (fact (name data-4) (value 2)) (fact (name data-5) (value 4)) (fact (name data-6) (value 3))) CLIPS&gt; (defrule find-max-value (fact (name ?name1) (value ?value1)) (not (fact (value ?value2&amp;:(&gt; ?value2 ?value1)))) =&gt; (printout t "Fact " ?name1 " is the maximum" crlf)) CLIPS&gt; (reset) CLIPS&gt; (run) Fact data-5 is the maximum CLIPS&gt; </code></pre> <p>The same basic approach also works if you bind all of the slot values needed for comparison and pass them into a function:</p> <pre><code>CLIPS&gt; (clear) CLIPS&gt; (deftemplate fact (slot name) (slot value)) CLIPS&gt; (deffacts test-data (fact (name data-1) (value 3)) (fact (name data-2) (value 1)) (fact (name data-3) (value 2)) (fact (name data-4) (value 2)) (fact (name data-5) (value 4)) (fact (name data-6) (value 3))) CLIPS&gt; (deffunction my-predicate (?value1 ?value2) (&gt; ?value1 ?value2)) CLIPS&gt; (defrule find-max-value (fact (name ?name1) (value ?value1)) (not (fact (value ?value2&amp;:(my-predicate ?value2 ?value1)))) =&gt; (printout t "Fact " ?name1 " is the maximum" crlf)) CLIPS&gt; (reset) CLIPS&gt; (run) Fact data-5 is the maximum CLIPS&gt; </code></pre> <p>Passing in a fact to the function, however, is problematic because you can't bind the pattern to a fact address inside a not conditional element. If the fact has a slot that serves as a unique identifier, you can use this to retrieve a pointer to the fact (although I wouldn't recommend this approach):</p> <pre><code>CLIPS&gt; (clear) CLIPS&gt; (deftemplate fact (slot name) (slot value)) CLIPS&gt; (deffacts test-data (fact (name data-1) (value 3)) (fact (name data-2) (value 1)) (fact (name data-3) (value 2)) (fact (name data-4) (value 2)) (fact (name data-5) (value 4)) (fact (name data-6) (value 3))) CLIPS&gt; (deffunction my-predicate (?fact1 ?fact2) (&gt; (fact-slot-value ?fact1 value) (fact-slot-value ?fact2 value))) CLIPS&gt; (defrule find-max-value ?fact1 &lt;- (fact (name ?name1)) (not (fact (name ?name2&amp;:(my-predicate (nth$ 1 (find-fact ((?fact2 fact)) (eq ?fact2:name ?name2))) ?fact1)))) =&gt; (printout t "Fact " ?name1 " is the maximum" crlf)) CLIPS&gt; (reset) CLIPS&gt; (run) Fact data-5 is the maximum CLIPS&gt; </code></pre> <p>What I would suggest doing is to use the fact query functions to iterate over the facts to find the maximum value:</p> <pre><code>CLIPS&gt; (clear) CLIPS&gt; (deftemplate fact (slot name) (slot value)) CLIPS&gt; (deffacts test-data (fact (name data-1) (value 3)) (fact (name data-2) (value 1)) (fact (name data-3) (value 2)) (fact (name data-4) (value 2)) (fact (name data-5) (value 4)) (fact (name data-6) (value 3))) CLIPS&gt; (deffunction my-predicate (?fact1 ?fact2) (&gt; (fact-slot-value ?fact1 value) (fact-slot-value ?fact2 value))) CLIPS&gt; (deffunction find-max (?template ?predicate) (bind ?max FALSE) (do-for-all-facts ((?f ?template)) TRUE (if (or (not ?max) (funcall ?predicate ?f ?max)) then (bind ?max ?f))) (return ?max)) CLIPS&gt; (reset) CLIPS&gt; (facts) f-0 (initial-fact) f-1 (fact (name data-1) (value 3)) f-2 (fact (name data-2) (value 1)) f-3 (fact (name data-3) (value 2)) f-4 (fact (name data-4) (value 2)) f-5 (fact (name data-5) (value 4)) f-6 (fact (name data-6) (value 3)) For a total of 7 facts. CLIPS&gt; (find-max fact my-predicate) &lt;Fact-5&gt; CLIPS&gt; (defrule find-max =&gt; (bind ?fact (find-max fact my-predicate)) (if ?fact then (printout t "Fact " (fact-slot-value ?fact name) " is the maximum" crlf))) CLIPS&gt; (run) Fact data-5 is the maximum CLIPS&gt; </code></pre> <p>Although CLIPS does not, many languages do support accumulation conditional elements which makes it easier to perform this type of calculation. For example, in Jess you can do this:</p> <pre><code>Jess&gt; (deftemplate fact (slot name) (slot value)) TRUE Jess&gt; (deffacts test-data (fact (name data-1) (value 3)) (fact (name data-2) (value 1)) (fact (name data-3) (value 2)) (fact (name data-4) (value 2)) (fact (name data-5) (value 4)) (fact (name data-6) (value 3))) TRUE Jess&gt; (if FALSE then 3 else 4) 4 Jess&gt; (defrule find-max-value ?c &lt;- (accumulate (bind ?max FALSE) (if (or (not ?max) (&gt; ?value ?max)) then (bind ?max ?value)) ?max (fact (value ?value))) =&gt; (printout t "The max is " ?c crlf)) TRUE Jess&gt; (reset) TRUE Jess&gt; (run) The max is 4 1 Jess&gt; </code></pre>
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