Hi Robert,
Sorry I didn't respond to this sooner -- your message was lost in a
flurry of other email and I'm just now finding it.
What's happening here is that your 'or' has two branches, one of
which defines a variable named '?val' (the first branch) and the
other of which doesn't (the second.) In the second branch, you're
matching the absence of facts, so obviously we can't later refer to
the contents of a slot in a fact which doesn't exist. Jess could do a
better job of data-flow analysis so that this is pointed out when the
rule is compiled, but as it stands, the error doesn't get noticed
until runtime. If it's that second branch that matches, then there's
no "?val" and you get an error when you try to examine the query
results.
So you need to rethink the rule and what you want to do with "?val".
On May 21, 2007, at 12:25 PM, Robert Kirby wrote:
While running Jess Version 7.0p1 12/21/2006, accessing defquery
results fails with a compound pattern that works with a defrule.
Bob Kirby
----------------
(deftemplate row
"A row in a test table."
(declare (ordered FALSE))
(slot primary (type SYMBOL))
(slot foreign (type SYMBOL)))
(deffacts rows
"Rows of a test table of primary and foreign keys."
(row (primary first) (foreign key1))
(row (primary second) (foreign unmatched)))
(deftemplate pair
"A pair of a key and a value."
(declare (ordered FALSE))
(slot key (type SYMBOL))
(slot val (type STRING)))
(deffacts pairs
"Pairs of keys and values including a default value."
(pair (key key1) (val val1))
(pair (key default) (val default-val)))
(defrule print-test-rule
"Test to print results from a rule"
(row (primary ?primary) (foreign ?foreign))
(or (pair (key ?foreign) (val ?val))
(and (not (pair (key ?foreign)))
(pair (key default) (val ?val))))
=>
(printout t "print-test-rule " ?primary " " ?foreign " " ?val
crlf))
(reset)
(run)
;;;print-test-rule second unmatched default-val
;;;print-test-rule first key1 val1
(defquery test-query
"A test query to assign defaults for foreign keys."
(row (primary ?primary) (foreign ?foreign))
(or (pair (key ?foreign) (val ?val))
(and (not (pair (key ?foreign)))
(pair (key default) (val ?val)))))
(deffunction print-test-query ()
"Run test-query"
(bind ?results (run-query* test-query))
(while (?results next)
(printout t "print-test-query "
(?results getString primary) " "
(?results getString foreign) " "
(?results getString val) crlf))
(?results close))
(print-test-query)
Jess reported an error in routine Context.getReturn
while executing (call ?results getString val)
while executing (printout t "print-test-query " (call ?results
getString primary) " " (call ?results getString foreign) " " (call ?
results getString val) crlf)
while executing (while (call ?results next) (printout t "print-
test-query " (call ?results getString primary) " " (call ?results
getString foreign) " " (call ?results getString val) crlf))
while executing deffunction print-test-query
while executing (print-test-query)
while executing (batch q.clp).
Message: No such variable val.
Program text: ( batch q.clp ) at line 1.
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Advanced Software Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
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