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567 discussions

Re: [cells-devel] Minor Celtk/Togl woes
by Luís Oliveira 16 Jun '06

16 Jun '06

On 2006-jun-15, at 20:58, Frank Goenninger wrote: >> Btw, Togl's CVS version (2.0 to be, apparently) doesn't have the >> following functions defined in togl.lisp: Togl_CreateFunc(), >> Togl_DisplayFunc(), Togl_ReshapeFunc(), Togl_DestroyFunc() and >> Togl_TimerFunc(). What's up with that? > > Hunh? Which CVS do you access? http://sourceforge.net/cvs/?group_id=519 The CVS repository has some 2 weeks old changes so I guess it's not too dead. Looking at the two gears.c examples, the interface changed from: Togl_CreateFunc(init); Togl_DestroyFunc(zap); Togl_DisplayFunc(draw); Togl_ReshapeFunc(reshape); Togl_TimerFunc(idle); Togl_CreateCommand("rotate", rotate); Togl_CreateCommand("position", position); to: Tcl_CreateObjCommand(interp, "init", init, NULL, NULL); Tcl_CreateObjCommand(interp, "zap", zap, NULL, NULL); Tcl_CreateObjCommand(interp, "draw", draw, NULL, NULL); Tcl_CreateObjCommand(interp, "reshape", reshape, NULL, NULL); Tcl_CreateObjCommand(interp, "idle", idle, NULL, NULL); Tcl_CreateObjCommand(interp, "rotate", rotate, NULL, NULL); Tcl_CreateObjCommand(interp, "position", position, NULL, NULL); -- Luís Oliveira http://student.dei.uc.pt/~lmoliv/

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[cells-devel] Minor Celtk/Togl woes
by Luís Oliveira 15 Jun '06

15 Jun '06

Hello, First off, I hope this is the right mailing list for Celtk issues. The first issue was easy. gui-geometry is missing an .asd file. (Attached is a simple .asd for it.) The second issue is that building Togl requires private Tcl/Tk headers that don't come with OSX's Tcl/Tk frameworks. This probably wan't the best way to do it but here's what I did: => Downloaded the Tcl distribution from http://www.opensource.apple.com/darwinsource/ => Copied the tk/tk8.4.7/generic/*.h and tk/tk8.4.7/macosx/*.h headers to /System/Library/Frameworks/Tk.framework/Versions/8.4/Headers/ => make. Copied libTogl1.7.dylib to /usr/lib => Changed togl.lisp's define-foreign-library. (patch attached) => Changed the pathnames that were pointing at c:\0dev\Celtk (patch attached) After this I can see spinning gears (though I can't seem to change their spinning speed) and lotsa widgets including a picture from back when Portugal was under a dictatorship and my parents didn't know each other. :-) Btw, Togl's CVS version (2.0 to be, apparently) doesn't have the following functions defined in togl.lisp: Togl_CreateFunc(), Togl_DisplayFunc(), Togl_ReshapeFunc(), Togl_DestroyFunc() and Togl_TimerFunc(). What's up with that? -- Luís Oliveira http://student.dei.uc.pt/~lmoliv/

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[cells-devel] Re: eager and lazy (brief)
by Ken Tilton 14 Jun '06

14 Jun '06

On 6/14/06, Andrew K. Wolven <awolven(a)yahoo.com> wrote: > > Do you know of any "gotcha"s for mixing eager and lazy evaluation of > attributes? No, but I do not use them much? I cc'ed the list because I believe Thomas uses them and he might have more experience. Do you have a specific scenario in mind that might be problematic? I can stare at the code and give you a rough guess. kt

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[cells-devel] I think it's a bug [was SOME vs The Ephemerals]
by Ken Tilton 14 Jun '06

14 Jun '06

If you have been following the drama, i broke Lars's chat log with this rule (somewhat revised): (chat-log:accessor chat-log :initform (c? (concatenate 'string (or .cache "") (some 'speech-of (participants-of self))))) SOME stops at the first non-nil speech, establishing no dependencies on the speech of any participant farther down the "participants-of" list. This is a problem, because speech-of is an ephemeral. It gets set to nil /without/ propagating after any non-nil value gets set and propagated. That is what ephemerals are all about, and I think that much is solid....... maybe not. We'll come back to this. Anyway, if someone farther down the list now says something, the rule does not run because it has no dependency on their speech. And the log misses an entry. Now I could just call this a user error ("Hey, Kenny! No dependency, no re-calc!") and wipe my hands of the whole mess, but I have been doing Cells for ten years and I had to debug in the internals for the first time in a lonnng time to figure this one out, so I think an unwritten law is being violated: normal, healthy Lisp code should transparently maintain dependencies automatically. deep background: if there is no way around this, so be it, we have an entry for a "gotchas" FAQ. But one thing that ruins supercool libraries is exactly this sort of violation of the principle of least surprise. So I want to see if the above code can be made to work. What I was thinking (until just now) was that any time a rule encountered an ephemeral, just after the ephemeral got reset, the rule should be rerun just to establish dependencies, not for its value. The code would be simple (famous last words): after resetting an ephemeral, iterate over all dependents of the ephemeral and call their rule, ignoring the return value. Weird, but I bet it works. The alternative is to implement the "reset ephemeral step" actually as a proper datapulse in which the ephemeral is set to NIL. Full propagation, including observers of the ephemeral. Boy, that sure weakens the ephemerality metaphor. :) Thoughts? Meanwhile, I will canvas real-world uses of ephemeral cells for inspiration. cheers, kenneth

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[cells-devel] Re: [PyCells] Chat Shocker!
by Ken Tilton 13 Jun '06

13 Jun '06

On 6/13/06, Phillip J. Eby <pje(a)telecommunity.com> wrote: > > At 12:22 PM 6/13/2006 -0400, Ken Tilton wrote: > >In the chat-log rule, look for anything: someone saying something, > someone > >leaving, someone arriving, and check them all each time. Before I > finsihed > >came the Shocker: omigod. What if two new participants get added at once? > >Or what if some state change propagates and causes two chat participants > >to exclaim "Omigod!"? Omigod. I cannot code (some 'speech (participants > >chat)). Omigod. Just as I have to check population changes /as well as/ > >speech acts, i have to check all speech acts!!!! You have no idea what I > >am yelling about, do you? > > I think I do. The problem is that you don't have "foreach" rules or > second-order events. Actually, I don't have /any/ Cells rules or syntax other than to create the Cells, classes, and observers. Inside a rule, one Just Writes Lisp. Someone once asked whether I had any such things as a special construct for iterating over a list, and I offered "some", which is a standard Lisp keyword. I pointed out that one of the big wins of Cells is precisely that one does not have to use special constructs to make the paradigm work -- that would weaken the system because then calling some 3rd-party library function that happens to visit other Cells would not establish dependencies. Never mind the hassle of forcing all /my/ library code to use Cells-ese to iterate over lists or just access variables. Make sense? Or did I misunderstand you? My mistake was simply trying to be too clever. I thought I knew how Cells worked. :) So I thought I could use SOME, which stops at the first non-nil value. That was dumb. yes, ephemerals get reset right away so only one can be /set/ at a time (since each set becomes a new moment in data-time), but Cells has evolved lately and ephemerals can start as non-nil or be ruled (hmm, I might have to test that last one <g>), so it is now possible for more than one ephemeral to hold a value during one "moment" as you say. Bots in a game might have a rule determining their speeches, and all decide to yell "Run away!" at the moment a rabbit appears. :) kenny In traditional rule-driven systems, you can > effectively say "for each X and Y that meet criterion Z, do A(X,Y)". If I > understand correctly, the only way to do this in Cells would be to put a > collection in a cell and then have a rule that created a collection of > corresponding objects from it, or at least transformed any changes in the > collection into ephemeral add/remove events. > > In other words, Cells itself only deals with first-order (zeroth order?) > changes to values and objects. It does not deal with *sets* of values or > objects. It seems to me that this is the underlying nature of the problem > you encountered. > > Probably the simplest way to solve it in the general case is with a stock > object that transforms a collection into plural add/remove events. Even > better, two of them: one that monitors a cell with a collection, and the > other an object that looks like a collection but exposes event > cells. These would be roughly equivalent to rule cells and input cells, > respectively, but for collections of values instead of individual ones. > >

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[cells-devel] Chat Shocker!
by Ken Tilton 13 Jun '06

13 Jun '06

[I thought I better share this with the PyCells crowd because it raises so many interesting issues.] In our last episode, we changed the Cells engine to rerun any rule dependent on an ephemeral after resetting the ephemral to NIL, so that rule's dependencies would reflect the world with the ephemeral slot as NIL. ie, it was a consistency issue: before this, the dependencies looked as if the ephemeral was still "on" even after it had been cleared. Inconsistency bad! The obvious downside: the rule gets run a second time (inefficient) and god help anyone putting side effects in their rule. OK, save that on the stack. I turned next to something else I noticed while playing with Lars's chat example: if a chatter was instantiated with a non-nil speech value, that speech did not make it into the chat log. The reason is simple: make chat make chatter with speech "hello world" [speech is ephemeral, so it is gone now] push chatter on to chat participants the chat-log cell sees null speech for new participant The solution brings up a Cells profundity: It is hard to be a little bit Cells. In the extended code sample below, we arrange for a proxy "joiner" slot to be watched by a /rule/ for the participants of a chat. Now what happens is: make chat set chat joiner to be (list name opening-remark) the participants rule runs and sees a new participant. and creates it with the speech initialized to the opening remark the participants slot propagates to the chat log, which sees the opening remark in the speech slot of the new participant (yeahh!) now at long last propagation has ended, and we process the 'ephemeral-reset' queueu, clearing the speech of the new participant The moral is first that, yes, an instance coming into existence is extremely interesting when it comes to internal consistency of state -- damn, we have not just changed state but /new/ state. That moral in turn gets back to the larger issue of it being hard to be "a little bit Cells"; the more we express declaratively, the better our models will work. Now let's start to look at why the article thread includes the word "Shocker". When I implemented the above it did not work at first. The opening remarks made it into the log, but I lost the annotations "So-and-so has entered the chat." What happened? Hoist on my own petard! The rule I had written for accumulating the chat log expected /either/ a speech or a new participant or a departed participant. I had now "fixed" things so that the new participant and its new speech were all part of one state change to the world. Doh! OK, fix the dumb assumption: In the chat-log rule, look for anything: someone saying something, someone leaving, someone arriving, and check them all each time. Before I finsihed came the Shocker: omigod. What if two new participants get added at once? Or what if some state change propagates and causes two chat participants to exclaim "Omigod!"? Omigod. I cannot code (some 'speech (participants chat)). Omigod. Just as I have to check population changes /as well as/ speech acts, i have to check all speech acts!!!! You have no idea what I am yelling about, do you? The last bit means I never ever should have been stopping at the first non-nil speech anyway. It was me being smart saying to myself "I know how Cells works, i will stop at the first". Dumb. the whole idea of (a) declarative and (b) transparency is to write the obvious code: iterate over all participants collecting any speech. meaning the fix I made to ephemerals to rerun rules, as plausible as it sounds (thine dependencies shalt match thine state) would not have been necessary. I like plausibility, but running the rule a second time is downright scary, let alone inefficient and unforgiving (to renegades who modify state inside rules), so out it comes. The really neat thing is that I am not through. The chat example eneded with one participant leaving the chat. before I made 'participants' a rule, that was done with an application (setf (participants chat) (remove....)) When I changed participants to be a rule, i forgot to change the depart-chat code. It worked. I was stunned, because Cells enforces a discipline: ruled Cells shall get their values only from an invocation of the rule. Then I remembered. This came up a couple of days ago and when I checked the "discipline" discovered that this rule was enforced only if *c-debug* was bound to t. I guess my thinking was that, in this case, other qualities of Cells still work. We do know who to notify of the change. But I was still thinking about being mean and closing this loophole. Until now. i kinda like this. :) There /is/ a declarative solution (change 'joiners' semantics to admit of an opcode (:join or :depart), but come on, we can be a /little/ sloppy, right? :) Here is the latest chat code. test function ending "oops" manifests the problem, ending "ok" shows the fix. kt (defpackage #:tu-some-ephemeral-uhoh (:use :cl :utils-kt :cells :tu-cells)) (in-package #:tu-some-ephemeral-uhoh) (defparameter *newline* (princ-to-string #\Newline)) (defmodel cells-chat (family) ;; kids slot can be partcipants ((chat-log :initarg :chat-log :accessor chat-log :initform (let (last-chatters) (c? (prog1 (apply 'concatenate 'string (or .cache "") (append (bwhen (lost-chatters (set-difference last-chatters (^kids))) (list (format nil "~{~a~} has left the chat~a" (mapcar 'username lost-chatters) *newline*))) (bwhen (new-chatters (set-difference (^kids) last-chatters)) (list (format nil "~a has joined the chat~a" (mapcar 'username new-chatters) *newline*))) (loop for p in (^kids) nconcing (bwhen (s (speech p)) (list (username p) ": " s *newline*))))) (setf last-chatters (^kids)))))))) (defmodel chatter (model) ((username :cell nil :accessor username :initarg :username :initform (error "chatter needs a `username'.")) (speech :cell :ephemeral :initform (c-in nil) :initarg :speech :accessor speech))) (defun tu-cells::tu-ephemeral-oops () (cells-reset) (let* ((chat (make-instance 'cells-chat)) (lars (make-instance 'chatter :fm-parent chat :speech (c-in "Hi, my name is Lars") :username "Lars"))) (push lars (kids chat)) (setf (speech lars) "Is anybody in here?") (push (make-instance 'chatter :fm-parent chat :speech (c-in "Hi, my name is Kenny") :username "Kenny") (kids chat)) (setf (speech lars) "Hi, Kenny. Cells are different.") (setf (speech (car (kids chat))) "Hi, Lars. That's for sure. Takes a while to adjust.") (setf (speech lars) "OK, I'll keep plugging") (depart-chat lars) (print (chat-log chat)))) (defun depart-chat (chatter) (setf (kids (fm-parent chatter)) (remove chatter (kids (fm-parent chatter))))) #+test (tu-cells::tu-ephemeral-oops) ; ; PROBLEM: The log is missing the initial speeches, because the ephemerals got reset before ; the instance was added to the particiapnts list. Solution: bring instantiation ; within the larger dataflow by making instantiation happen inside a rule for kids. ; (defmodel joinable-able (cells-chat) ((joiners :cell :ephemeral :initform (c-in nil) :initarg :joiners :accessor joiners)) (:default-initargs ; ; SOLUTION: the initial speech will stay around until the entire state change ; propagation has completed, including updating the chat log which has ; a dependency on the chat 'kids'. The new chatter gets instantiated as ; part of this rule, which then propagates to the chat-log, which sees the ; speech. That is ephemeral, but ephemerals do not get reset until after ; all propagation in one datapulse (ephemeral reset has its own queueu). ; :kids (c? (the-kids (loop for (name opening-remark) in (^joiners) collecting (make-kid 'chatter :username name :speech (c-in opening-remark))) .cache)))) (defun join-chat (chat &rest names) (setf (joiners chat) (loop for n in names collecting (list n (format nil "Hi, my name is ~a" n)))) (subseq (kids chat) 0 (length names))) (defun tu-cells::tu-ephemeral-ok () (cells-reset) (let ((chat (make-instance 'joinable-able)) lars kenny) (setf lars (car (join-chat chat "Lars"))) (setf (speech lars) "Is anybody in here?") (setf kenny (car (join-chat chat "Kenny"))) (setf (speech lars) "Hi, Kenny. Cells are different.") (setf (speech kenny) "Hi, Lars. That's for sure. You seem to be coming up to speed nicely.") (setf (speech lars) "OK, I'll keep plugging") (depart-chat lars) (join-chat chat "Peter" "Paul" "Mary") (print (chat-log chat)) (values))) #+test (tu-cells::tu-ephemeral-ok)

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[cells-devel] chat-server using cells?
by Lars Rune Nøstdal 13 Jun '06

13 Jun '06

Hi, I'm trying to figure out how to design a chat-server using Cells. This doesn't work, but this is what I've come up with: (defpackage CellsChat (:use :cl :cells)) (in-package :CellsChat) (defparameter *newline* (princ-to-string #\Newline)) (defmodel CellsChat () ((username :cell nil :accessor username-of :initarg :username :initform (error "CellsChat needs a `username'.")) (text-box :accessor text-box-of :allocation :class :initform (c-in "")) (participants :cell nil :accessor participants-of :allocation :class :initform nil))) (defmethod initialize-instance :after ((chat CellsChat) &key) ;; New user joins the conversation. (push chat (participants-of chat)) ;; New user wants to see what's been going on recently. (updateTextBox chat)) (defmethod updateTextBox ((chat CellsChat)) ;; Show conversation till now. (format t "(text-box-of ~A): '~A'~%" (username-of chat) (text-box-of chat))) (defobserver text-box ((chat CellsChat)) ;; Update interface of each participant whenever ;; `text-box' changes (for whatever reason). (dolist (participant (participants-of chat)) (updateTextBox participant))) (defmethod say ((chat CellsChat) (what string)) (setf (text-box-of chat) (concatenate 'string (text-box-of chat) (username-of chat) ": " what *newline*))) (defmethod part ((chat CellsChat)) ;; User leaves the conversation. (setf (participants-of chat) (delete chat (participants-of chat)))) -- Mvh, Lars Rune Nøstdal http://lars.nostdal.org/

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[cells-devel] Small change
by Ken Tilton 10 Jun '06

10 Jun '06

I just modified md-slot-value-assume to test for "no news" just a wee bit sooner within the function. The regression test passes, as does Celtk's lotsa-widgets test. But I thought I would warn users in case they update from CVS soon. My concern is that I do not know why I had it so late in the past -- probably because the unnecessary actions taken were so inexpensive -- so maybe it was where it was for a reason. But as I said, all the tests pass as well as real-live Celtk code (which itself exercises Cells pretty well) so it looks OK. kt

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[cells-devel] Gmane archiving for cells-devel?
by Ken Tilton 10 Jun '06

10 Jun '06

I am not much up on this Gmane thingy, but apparently this list is headed that way (and this message exists just to trigger activation so i can be sure). kt

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[cells-devel] Re: Question about Cells; defobserver for both I and O
by Ken Tilton 09 Jun '06

09 Jun '06

Lars Rune Nøstdal wrote: > Hi Lispers, > Ok, starting to get the hang of this, but I'm having a small issue > maybe you guys could help me with. > > I'm playing with some AJAX-stuff and .. hm .. not sure how to explain > this proper, but .. Fair warning: I have never programmed a Web app, barely done anything with HTML, and understood almost nothing of what you wrote. :) But this (check me: input form field initialized from a database record field, then overwritten by user so data must flow the other way back to the DB?) happens all the time in standalone apps, so... > > I have an INPUT-element (HTML) that can be used for both input of data > (client-initiated) and output of data (server-initiated), and I'd like > to block the observer so it does not react on input from the client and > tries to re-update the element .. > > ..or maybe "blocking" the observer isn't right at all, maybe I'm going > about this the wrong way..? As I said, this comes up all the time, and what you tried is the tempting automatic flow: DB(existing value -> Input(as initial value) -> DB(new value) Your code is what I think about writing even after ten years of using Cells. So how do we break the cycle? There are several ways I have handled this. 1. In the slot definition, specify: (value ...etc... :unchanged-if 'string=) You will still make the return trip to set the input field unnecessarily, but that will be an NOP because the new value will be seen as unchanged, stopping propagation (including calling observers). The default test is EQL and it is easy in even simple code for 'string= but un-EQL strings to arise and start cycling. To avoid even the beginnings of a roundtrip, hey, have the observer take a peek at where it is about to write and decide if it needs to. Not as much fun as letting Cells worry about it, but this one observer (I gather) is handling all the HTML input fields, so...? Now I revert to my earlier disclaimer about being Web-ignorant: I think The Right Answer overall will be decided by the exact nature of the Web stuff, so I will just continue dumping alternatives 2. Does the DB flow to the form only when the form is opened? If so, the HTML input fields can have a something another Cells user just requested: a rule that runs once at initialization time and then becomes a /Cells/ input. ie, the slot starts as c-formula but then becomes c-input. (No dependencies are recorded during the initial rule invocation.) Only the HTML input field has an observer writing back to the corresponding DB field. Now if only cells had some frickin decent doc I could tell you the syntax. Maybe: (c-formula (:inputp t) <code to lookup value for this field>) If that is what you settle on and it does not work I will research further. 3. if you are in a multi-user environment or for any other reason need to update the form programmatically at the same time the user is typing, well, things will be pretty exciting for the user <g>, and it may be time to consider the failsafe: do not try to use Cells dataflow where the application really needs to decide the dataflow. An application flow will have to be concocted, hopefully facilitated by Cells, but always keep in mind that the functionality might dictate more savvy than the Cells changed/not-changed propagation smarts. hth, ken > Here is some code: > > > (defobserver value ((value-attribute ValueAttribute)) > (cells::trc "ValueAttribute changing from" old-value :to new-value) > (terpri) > ;; Update the value-attribute of the HTML-element on the client-side. > (setAttribute (parent-of value-attribute) > (name-of value-attribute) > "value" > (princ-to-string (value-of value-attribute)))) > > (defmethod onkeyup ((value-attribute ValueAttribute) (parent Container) > &rest event-args) > (format t "onkeyup: ~A~%" (fifth event-args)) > (setf (value-of value-attribute) > (first event-args))) > > > `onkeyup' is called from the client-side and since (setf value-of ..) > triggers the observer for the slot `value', it tries to "redraw" what's > already on the client-side. > -- Cells: http://common-lisp.net/project/cells/ "I'll say I'm losing my grip, and it feels terrific." -- Beaming husband to scowling life, New Yorker cartoon

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