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(default 80)))
CLIPS> (defrule happy_relationship
(prospect (name $?name) (assets ?net_worth) (age ?months))
=>
(printout t "Prospect: " ?name crlf ; Note: not ?name
?net_worth crlf
?months " months old" crlf))
CLIPS> (deffacts duck-bachelor
(prospect (name Dopey Wonderful) (assets rich) (age 99)))
CLIPS> (reset)
CLIPS> (run)
Prospect: (Dopey Wonderful)
rich
99 months old
CLIPS>
In the output, the parentheses around Dopey's name are put in by CLIPS to indicate
that this is a multislot value. If you compare the output from this multislot version to the
single-slot version, you'll see that the double quotes around "Dopey Wonderful" are
gone. The name slot is not a string in the multislot version, so CLIPS treats the name as
two independent fields, Dopey and Wonderful.
What's in a Name
Deftemplate greatly simplifies accessing a specific field in a pattern because the desired
field can be identified by its slot name. The modify action can be used to retract and
assert a new fact in one action by specifying one or more template slots to be modified.
As an example, consider the following rules which show what happens when
duck-bachelor Dopey Wonderful loses all his fish buying Donald Duck posters and
banana fishsplits for his new duckette, Dixie.
CLIPS> (undefrule *)
CLIPS>
(defrule make-bad-buys
?prospect <- (prospect (name $?name)
(assets rich)
(age ?months))
=>
(printout t "Prospect: " ?name crlf ; Note: not ?name