JESS: Scoping Question
Hi Ernest: I came across a strange feature of Jess as a result of a typing error. It appears as though Jess uses dynamic scoping -- any variables defined in a rule are visible in any functions called by the RHS of the rule. I looked for references to this in the book and the manual but couldn't find anything. Is this the expected behaviour? (This is just a curiosity question.) Thanks David (deftemplate person (slot name) (slot age)) (deffacts initialFacts (person (name bill) (age 20)) (person (name will) (age 25)) (person (name dill) (age 25)) (person (name jill) (age 22)) ) (defrule findOldest ?f - (person (age ?max)) (not (person (age ?less:( ?less ?max = (my-function) ) (deffunction my-function () (printout t crlf Processing fact (?f toString) crlf) (printout t crlf Max age is ?max crlf) (printout t crlf Max age is ?f.age crlf crlf) ) (reset) (run) (facts)
RE: JESS: Scoping Question
Since control structures are functions in Jess, the ability for a function to peek from one stack frame to another is important. I could have implemented this using some kind of special form or keyword -- like the Tcl uplevel function -- but in the first go-round, I think I just took the easy way out, and this behavior has stuck ever since. Note that it's read-only by default: binding a value to a variable in a deffunction creates a new variable in the local scope. That's why recursive functions are possible. From: owner-jess-us...@sandia.gov [mailto:owner-jess-us...@sandia.gov] On Behalf Of David Scuse Sent: Wednesday, November 09, 2011 11:43 AM To: jess-users Subject: JESS: Scoping Question Hi Ernest: I came across a strange feature of Jess as a result of a typing error. It appears as though Jess uses dynamic scoping -- any variables defined in a rule are visible in any functions called by the RHS of the rule. I looked for references to this in the book and the manual but couldn't find anything. Is this the expected behaviour? (This is just a curiosity question.) Thanks David (deftemplate person (slot name) (slot age)) (deffacts initialFacts (person (name bill) (age 20)) (person (name will) (age 25)) (person (name dill) (age 25)) (person (name jill) (age 22)) ) (defrule findOldest ?f - (person (age ?max)) (not (person (age ?less:( ?less ?max = (my-function) ) (deffunction my-function () (printout t crlf Processing fact (?f toString) crlf) (printout t crlf Max age is ?max crlf) (printout t crlf Max age is ?f.age crlf crlf) ) (reset) (run) (facts)
Re: JESS: Scoping Question
That makes perfect sense. Thank you. - Original Message - From: Friedman-Hill, Ernest To: jess-users Sent: Thursday, November 10, 2011 2:15 PM Subject: RE: JESS: Scoping Question Since control structures are functions in Jess, the ability for a function to peek from one stack frame to another is important. I could have implemented this using some kind of special form or keyword -- like the Tcl uplevel function -- but in the first go-round, I think I just took the easy way out, and this behavior has stuck ever since. Note that it's read-only by default: binding a value to a variable in a deffunction creates a new variable in the local scope. That's why recursive functions are possible. -- From: owner-jess-us...@sandia.gov [mailto:owner-jess-us...@sandia.gov] On Behalf Of David Scuse Sent: Wednesday, November 09, 2011 11:43 AM To: jess-users Subject: JESS: Scoping Question Hi Ernest: I came across a strange feature of Jess as a result of a typing error. It appears as though Jess uses dynamic scoping -- any variables defined in a rule are visible in any functions called by the RHS of the rule. I looked for references to this in the book and the manual but couldn't find anything. Is this the expected behaviour? (This is just a curiosity question.) Thanks David (deftemplate person (slot name) (slot age)) (deffacts initialFacts (person (name bill) (age 20)) (person (name will) (age 25)) (person (name dill) (age 25)) (person (name jill) (age 22)) ) (defrule findOldest ?f - (person (age ?max)) (not (person (age ?less:( ?less ?max = (my-function) ) (deffunction my-function () (printout t crlf Processing fact (?f toString) crlf) (printout t crlf Max age is ?max crlf) (printout t crlf Max age is ?f.age crlf crlf) ) (reset) (run) (facts)
JESS: Ignore slots when matching lhs of rules
Hi everyone, I am trying to match the lhs of a rule using a template that has 112 slots that is defined from a Java class. Here is the template definition (from show-deftemplates): (deftemplate MAIN::unit $JAVA-OBJECT$ eisbot.proxy.model.Unit (declare (from-class eisbot.proxy.model.Unit))) Now every time that I encounter a unit object in my application I define an instance of the unit to Jess from Java: engine.defclass(unit, eisbot.proxy.model.Unit, null, true); (I only do this the first time) Unit unit = //retrieve a unit engine.definstance(unit, unit, false); All of this above is working as it should be, but now when I try to match a unit in a rule I am having trouble: String unitSeen = (defrule unitSeen + (unit (ID ?id) (typeID ?typeID)) + = + (printout t \Unit seen with ID: \ ?id crlf)); engine.executeCommand(unitSeen); The problem is that the Unit class has 112 attributes, I am only listing two ID and typeID, and there are probably only another handful that I care about and need to use. Is there any way to ignore the rest of the slots in the template, matching only on a few slots? Goal: The main goal of what I am trying to is that when I encounter a Unit in my game application, I want to assert that unit object to Jess as a fact, then match rules on the existence of a Unit. Right now I only want to match on the existence of ANY unit, but later on the matches will be more specific. Any help would be most appreciated. Thanks. Hunter McMillen
