November 2003 - cells-devel - mailman3.common-lisp.net

[cells-devel] Doc?
by Kenny Tilton 10 Nov '03

10 Nov '03

I spent the weekend working on resurrecting Cello, the (in principle) portable GUI built atop Cells. The only changes planned now are backing off various forkings and letting especially FreeGlut alone. That much worked pretty easily, and after noticing that my intended new font engine is actually a C++ library, well, I could make it work since I have my own C DLL anyway to get to the OS fonts, but for now I think I'll keep things simple and just go with my own glue to the OS font functionality. Stuff I am reading says this may be optimal anyway, because it can segue into texture fonts, apparently the best for performance and scalability, and even anti-aliasing. So Cello (such as it is) looks to be under control, and so I want to get back to Cells and do up some documentation. The first thing will be a write-up of a nice little use case to which Cells were applied. I keep promising to do that, and tomorrow I will really try to Just Do It. Then what? Something that looks like a reference? Or a series of tutorials? Other? kenny -- http://tilton-technology.com Why Lisp? http://alu.cliki.net/RtL%20Highlight%20Film Your Project Here! http://alu.cliki.net/Industry%20Application

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[cells-devel] Minimal web page, CVS
by Thomas F. Burdick 08 Nov '03

08 Nov '03

I put up a minimal webpage, that points people here and to the zip file. I'll be putting the code in CVS shortly. -- /|_ .-----------------------. ,' .\ / | No to Imperialist war | ,--' _,' | Wage class war! | / / `-----------------------' ( -. | | ) | (`-. '--.) `. )----'

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[cells-devel] [ANNC] Caveat FTPer, Cells031108 now available via FTP (CVS RSN)
by Kenny Tilton 08 Nov '03

08 Nov '03

I /think/ I did it right: ftp://common-lisp.net/pub/project/cells See cells-read-me.txt for instructions, which are basically: Edit build.lisp and adjust a couple of config things. Save. (load "build.lisp") yell if there's a problem. kenny -- http://tilton-technology.com Why Lisp? http://alu.cliki.net/RtL%20Highlight%20Film Your Project Here! http://alu.cliki.net/Industry%20Application

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[cells-devel] Re: It's not a feature, it's a bug
by Kenny Tilton 07 Nov '03

07 Nov '03

Thomas F. Burdick wrote: >Kenny Tilton writes: > > Turns out I /do/ try to reset an ephemeral initialized to (CV <not > > nil>), but I only reset the cached value slot of the cell, not the > > slot-value per se. And the slot-value is the place the accessor looks > > for a value. The cache is just used for other stuff. Ah, the hazards of > > redundant representation. > >Writing a simple KR<-->CLOS bridge was easy, but not subtly screwing >up the duplicated information was kind of a headache, so I can sympathize. > > > Anyway, I think we are agreeing to let ephemeral + (CV <whatever>) > > signify that <whatever> is the value to revert to after a later > > ephemeral datachange for such a slot. Hmmm, let me thnk about this. I > > actually saw this bug and might have it in a do-list somewhere. I think > > it came up because I wanted a non-nil initial value for a nil-based > > ephemeral slot at make-instance-time. > >Yep, we're in agreement. This would be very useful for ephemeral >slots that take on numeric values, and for interacting well with type >declarations. In SBCL, declarations = assertions (CMUCL too, but SBCL >takes it more seriously), so you can do something like: > > (defclass foo () ((a :accessor foo-a :type fixnum))) > >and if you try to set an A slot to something other than a fixnum, >you'll get a runtime error. > Good lord. Do they know CL is short for Common Lisp? Tell me they get huge runtime performance benefits from this sacrilege. Actually, there is a problem here. Currently Cell structures land in the slot during make-instance (when I had a MOP-based implementation I shunted Cells bound for a slot over to the .cells internals slot before they ever got to the slot, by placing an around method on (setf slot-value-using-class)). Possibly I can do the same with an around meth on shared-initialize, but till then SBCL will likely not be happy with a Cell in a slot typed numeric. Well, we'll put this in the hopper, but I propose we give higher priority to me documenting the system and getting Cello going. And I think I do want to make the resumed base value (what /do/ we call that?) of an ephemeral a distinct attribute, so as not to shadow the semantics of an instance being initialized with an ephemeral slot initialized, say, (CV 2) with baseline value zero. > Plus, you get compile-time warnings if >Python's type inference shows that A could be set to a non-fixnum. > >One problem with Cell-as-is on SBCL, is that the type checking only >happens when you use the accessor function, not SLOT-VALUE. This is >probably best considered a bug in SBCL's PCL, but it has the following >unfortunate result: > > * (defmodel foo () > ((x :initform (cv 0) :accessor get-x :type fixnum) > (10x :initform (c? (* 10 (get-x self))) :accessor get-10x :type fixnum))) > STYLE-WARNING: redefining SHARED-INITIALIZE :AFTER (FOO T) in DEFMETHOD > Hey, SBCL is creating an after method on shared-initialize? > STYLE-WARNING: redefining GET-X (FOO) in DEFMETHOD > STYLE-WARNING: redefining (SETF GET-X) (T FOO) in DEFMETHOD > STYLE-WARNING: redefining GET-10X (FOO) in DEFMETHOD > STYLE-WARNING: redefining (SETF GET-10X) (T FOO) in DEFMETHOD > <heh-heh> I keep wondering my I do not get "get-10x defined twice in foo.lisp" et al, but I do not. > > #<STANDARD-CLASS FOO> > * (setf >>foo (make-instance 'foo)) > > FOO > * (get-10x >>foo) > > 0 > * (setf (get-x >>foo) most-positive-fixnum) > > 536870911 > * (get-10x >>foo) > > 5368709110 > * (typep * 'fixnum) > > NIL > > Gee, what /is/ the type? >In reverse order of simplicity, the best way to solve this would be to >fix SBCL; > Have you asked the SBCL crowd whether they are set on slot-value being type-ignorant? >the second best way would be to either have Cells use >:around methods, instead of redefining the primary methods, then >invoke the proper next-method machinery > That scares me.in the abstract, tho I cannot point to any evil consequence, I just think one will arise in due course because it strikes me as a kluge. >-- or, have Cells propagate >the type declaration to its new method definitions. > That should be easy, and sounds Deeply Correct. I am already looking at the slot definition name to get reader and writer names, may as well grab the type if any. So what's the syntax for declaring a /return/ type? And the synatx on the setf side as well. >Since we've got >eager data propogation, it would be nice to get the type errors with >the stack still intact. Obviously, though, this can wait for a bit >(although I might make it one of my higher priorities once Cells is in >CVS). > I hear a vote for early CVS. :) > > Tell you what, I owe common-lisp.net a release, let me just fix the bug > > so a (cv 2) does get reset as advertised and the doc is accurate, then > > we can study this. I might want to change the syntax from :cell > > :ephemeral to ":cell t :ephemeral-resumes <whatever>" where by the new > > scheme the :cell t is unnecesary since that's the default, but anyway. > > Then :ephemeral-resumes is a two-fer, it gives you ephemrality as well > > as specifying the value to resume after a change. > >Hmm, :ephemeral-resumes seems like a weird name. Maybe >:ephemeral-default ? Actually, I think it would be better to stick >with the :cell :ephemeral :initform ( syntax > In RMS (an ISAM) one could specify that spaces or all zeros or whatever were the NULL_VALUE for an alternate key, meaning "if this is my value for this indexed field, just leave me the hell out of that index; i cannot be found that way". This was crucial where an indexed field was populated by only one or two percent weirdo records. Without NULL-VALUE, you get a million records with the same duplicate value, and an insertion could take 30 seconds as RMS read through a vast index tree looking for the place to insert. How is: :cell :ephemeral :c-null-value 0 :initform (cv 0) I just feel kinda bad making them type in the initform when at this point DEFMODEL has enough info to auto-supply that (and I do frequently neglect to code in (cv nil) on ephemerals. Should we add that nicety? Do we need a warning if they say :c-null-value and they do not say :ephemeral? The parallel error went unnoticed on an RMS file with consequences you would not believe. The nice thing about the suggested alternative :ephemeral-resumes 0 (with :cell t by default,and of course a better name) is that it eliminates the redundant declaration kenny -- http://tilton-technology.com Why Lisp? http://alu.cliki.net/RtL%20Highlight%20Film Your Project Here! http://alu.cliki.net/Industry%20Application

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[cells-devel] A test and a notification: it's two articles in one!
by Kenny Tilton 07 Nov '03

07 Nov '03

(1) Lessee if this bad boy is working. (2) I am continuing to get excellent traffic re Cells at my private address. I will reply here to encourage the switchover. (3) Some of that excellent traffic calls for tweaks to Cells. I better upload a zip of what I have so far ASAP, or newbies won't have anything to look at at all. CVS can probably wait until the next release. (4) The next release will possibly refine ephemerals a little and will try to make life with SBCL better. kenny -- http://tilton-technology.com Why Lisp? http://alu.cliki.net/RtL%20Highlight%20Film Your Project Here! http://alu.cliki.net/Industry%20Application

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