August 1998 - XEmacs-Beta - XEmacs Mailing List Archives

Re: Macros: Scheme vs Common Lisp 26 years, 3 months

Michael Sperber

>>>>> "Holger" == Holger Schauer <schauer(a)coling.uni-freiburg.de> writes: >>>>> "MS" == Michael Sperber schrieb am 19 Aug 1998 09:36:44 +0200: Holger> Interestingly there is a difference whether you quote bar or not: Holger> (setq bar 23) Holger> (defmacro foo () 'bar) Holger> (let ((bar 42)) (foo)) => 42 Holger> (defmacro foo () bar) Holger> (let ((bar 42)) (foo)) => 23 Holger> So, you can get the behaviour you want, you just need to know Holger> how ;-) No, this is different. When you don't quote bar, you get the value of the binding at macro *definition time*. I want the value of the binding at macro *use time*. If you do a (setq bar 47) between definition and use, you'll see the difference. MS> I don't understand that last sentence. If I create a package, MS> and I put abstractions in that package, may they be syntactic or MS> semantic abstractions, I want those abstractions to be able to MS> access bindings in the package. Holger> Which is of course possible if you use packages in CL ;-) Yeah, if I use explicit qualification, which amounts to not using the package system at all. MS> Absolutely. I just fucked up the example. In the case of MS> special variables, you do want the macro to refer to the MS> dynamically bound version. Holger> I was under the impression that setq at the toplevel would Holger> automagically be declared special, but obviously this is not true for Holger> (or required by) the current ANSI standard as readable in the Holger> HyperSpec. (CMUCL does this, IIRC, Allegro CL doesn't). So what's the politically correct way to define top-level bindings which are not special in Common Lisp? Holger> PS: What about my second question: is it possible to obtain the CL Holger> behaviour in Scheme ? I'm not sure what exactly you mean. If you mean: "Can I access bindings not within the scope of a macro from the macro?" ... then the answer is no, just as you can't access bindings not within the scope of an abstraction from within the abstraction. You shouldn't be able to. If you want something equivalent to dynamic binding, you generall use lexical scoping plus dynamic assignment in Scheme, in which case the macro will do what you want. -- Cheers =8-} Chipsy Friede, Völkerverständigung und überhaupt blabla

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Re: Macros: Scheme vs Common Lisp 26 years, 3 months

Michael Sperber

>>>>> "Craig" == Craig Lanning <CraigL(a)internetx.net> writes: Craig> At 11:08 AM 8/18/98 +0200, Michael Sperber [Mr. Preprocessor] Craig> wrote: [ ... ] Craig> Maintaining hygiene this way is not really much worse than writing the Craig> macro in the first place. Urmh, yes it is. So there :-) >> Also, a macro might refer to bindings whose names are free in the >> macro definition. There's no guarantee that you'll get the same >> bindings for a use that you referred to at the point of definition. Craig> Most of the macros that I write are used at top level so lexical bindings Craig> aren't a big problem. Yes they are, because the macro may refer to other toplevel lexical bindings. I just posted (and corrected ...) and example about this. It seems to me (I may be wrong) Common Lispers inherently avoid situations where a macro lead to binding problems precisely because they lead to these problems. In Scheme, I write macros which would cause problems in Common Lisp (but don't in Scheme) all the time. Craig> I don't see how using macroexpand limits the complexity of macros that one can Craig> write. (c-sh-M expands one level, m-sh-M expands all levels) I use macroexpand Craig> to make sure that the macro expands into the code that I intended. Getting Craig> the right things quoted can be very tricky. Exactly. Which is why in the Scheme macro system, the macro metalanguage is not the same as the object language. No quoting you may get wrong. Craig> This is a macro that I use to expand an abstract object definition Craig> into all the necessary class and method definitions for the application: Craig> (defmacro DEFINE-ENTITY (name supertypes attributes &body options) Craig> (declare #+Genera (zwei:indentation 2 7 3 1) Craig> (ignore options)) Craig> `(progn Craig> (defclass ,name ,(or supertypes '(entity)) Craig> ,(loop for (name nil opt?) in attributes Craig> collect `(,name Craig> :accessor ,name Craig> ,＠(unless opt? '(:initform nil)) Craig> :initarg ,(intern (cl:string name) :keyword))) Craig> ) Craig> ,＠(loop for (aname type opt?) in attributes Craig> as bname = (intern (format nil "~A-BOUNDP" aname)) Craig> as muname = (intern (format nil "~A-MAKUNBOUND" aname)) Craig> as ptype = (if (listp type) Craig> `(clim:sequence ,(cl:second type)) Craig> type) Craig> append `((defmethod ,bname ((obj ,name)) (slot-boundp obj ',aname)) Craig> (defmethod ,muname ((obj ,name)) (slot-makunbound obj ',muname)) Craig> (defmethod EDIT-ATTRIBUTE ((obj ,name) (attrib (eql ',aname)) stream Craig> &rest options) Craig> (values Craig> (apply #'clim:accept ',(if opt? `(clim:null-or-type ,ptype) ptype) Craig> :stream stream options) Craig> ',opt?)))) Craig> (defmethod %%ATTRIBUTES append ((obj ,name)) Craig> '(,＠(loop for (aname) in attributes collect aname))) Craig> ) Craig> ) Craig> The symbols STRING and SECOND are qualified because they have been shadowed Craig> in this package. You will note that there are no uses of MAKE-SYMBOL or Craig> GENSYM in this macro. Would hygienic macros have made writing this any Craig> easier? There happen to be no hygiene issues here. (Good for you ... :-} ) So, no, hygiene per se would not have made it easier. However, pattern matching (instead of using s-exprs to represent expressions) would have saved you all the quasiquoting trouble. Here's an example in Scheme (taken from the Scheme 48 distribution) which doesn't use hygiene, but does use pattern matching. It defines macros for defining records in a convenient syntactic form: ; Copyright (c) 1993, 1994 by Richard Kelsey and Jonathan Rees. ; Copyright (c) 1996 by NEC Research Institute, Inc. See file COPYING. ; This is JAR's define-record-type, which doesn't resemble Richard's. ; There's no implicit name concatenation, so it can be defined ; entirely using syntax-rules. Example: ; (define-record-type foo :foo ; (make-foo x y) ; foo? - predicate name is optional ; (x foo-x) ; (y foo-y) ; (z foo-z set-foo-z!)) (define-syntax define-record-type (syntax-rules () ((define-record-type ?id ?type (?constructor ?arg ...) (?field . ?field-stuff) ...) (begin (define ?type (make-record-type '?id '(?field ...))) (define ?constructor (record-constructor ?type '(?arg ...))) (define-accessors ?type (?field . ?field-stuff) ...))) ((define-record-type ?id ?type (?constructor ?arg ...) ?pred ?more ...) (begin (define-record-type ?id ?type (?constructor ?arg ...) ?more ...) (define ?pred (record-predicate ?type)))))) ; Straightforward version (define-syntax define-accessors (syntax-rules () ((define-accessors ?type ?field-spec ...) (begin (define-accessor ?type . ?field-spec) ...)))) (define-syntax define-accessor (syntax-rules () ((define-accessor ?type ?field ?accessor) (define ?accessor (record-accessor ?type '?field))) ((define-accessor ?type ?field ?accessor ?modifier) (begin (define ?accessor (record-accessor ?type '?field)) (define ?modifier (record-modifier ?type '?field)))) ((define-accessor ?type ?field) (begin)))) Note the absence of quasiquote/unquote/unquote-splicing. Here's macro which makes use of hygiene: (define-syntax define-for-each (syntax-rules () ((define-for-each foo-for-each foo-length foo-ref) (define (foo-for-each proc v) (let ((z (foo-length v))) (do ((i (- z 1) (- i 1))) ((< i 0) #f) (proc (foo-ref v i)))))))) Note that (define-for-each bar-for-each (lambda (dummy) z) (lambda (dummy) i)) (admittedly a contrived use) does the right thing. >> Let's say I have this: >> >> (defvar bar 23) [ I meant (setq bar 23) ] >> >> and I want to refer to bar (that is, the above binding) in a macro >> body: >> >> (defmacro foo () 'bar) >> >> ... but I do: >> >> (let ((bar 42)) (foo)) >> => 42 >> >> This violates lexical scoping. Craig> I can't think of any practical use for this construct. When I Craig> reference a global binding this way in a macro, it is because I Craig> wanted to rebind it for other code within the body of the macro. Then you're not referencing the same global binding. When I reference a global binding within a macro's lexical scope, I want to reference that binding. Period. -- Cheers =8-} Chipsy Friede, Völkerverständigung und überhaupt blabla

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Work in progress - better list processing 26 years, 3 months

Martin Buchholz

The current list traversing functions in XEmacs, like Fmemq, have a few problems relating to circular list checking. The use of the QUIT macro in each loop iteration allows the user to get out of an infinite loop. This accesses a global volatile variable, and since modern processors are `I/O-bound', this is a significant performance hit. How much, you ask? I actually benchmarked this, and the numbers are between 20% and 40%, depending on processor and compiler. Your mileage will vary, but Linux users will probably see a 25% win on ALL list traversing functions. The other problem is relying on the user to explicitly abort an infinite loop. Better is to signal a circular-list error. The algorithm I use is tortoise/hare with head start. The hare is doing the normal work of the loop. After a thousand iterations, we suspect there might be a circular list, so we start up the tortoise. The only overhead for `normal' lists is integer increment and comparison with a constant, which is `free' on today's processors. While I was at it, I fixed XEmacs to not lock up when printing a circular list. DON'T TRY THIS ON YOUR CURRENT XEMACS: (progn (setq x '(nil)) (setcdr x x)) ==> (nil ... <circular list>) Martin

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Question about Elisp packages 26 years, 3 months

lbudney＠pobox.com

Hello, Xemacs gurus! Amir Katz referred me to this list when I asked him a question. I am the maintainer of Mailcrypt, which is struggling to work correctly on Xemacs (I use FSF Emacs *blush*). If anyone can answer my question, please CC me since I don't subscribe to this list. The question is: should elisp packages be compiled with the "--vanilla" option (or "-q -no-site-file" for older Xemacs)? Is there a traditional answer? Are there compelling arguments either way? The original mailcrypt does not turn off site customization, and I don't have any to turn off. However, Amir suggested that I use the "--vanilla" option. Any suggestions? Thanks in advance, Len.

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[Success] XEmacs 21.0-pre10 "Erzgeberg" on Digital UNIX 4.0D 26 years, 3 months

Kevin Oberman

# ./configure -without-gcc --with-gnu-make --cflags '-fast -std' --site-include\ s=/usr/local/include --with-site-lisp Built the kit from patches using DEC C and gnu make. No problems, but one oddity... The initial sizing of purespace was VERY large. the build re-dumped with increasingly small purespace sizes unit it fit, but I don't recall every seeing this before. Purespace usage: 134856 of 1689000 (8% -- 1517k wasted). Purespace usage: 1052480 of 1689000 (62% -- 621k wasted). Purespace usage: 1052480 of 1052480 (100%). Several minor errors were detected in dgif_lib.c. cc: Warning: dgif_lib.c, line 113: In this statement, the referenced type of th\ e pointer value "Buf" is "unsigned char", which is not compatible with "const c\ har". if (strncmp(GIF_STAMP, Buf, GIF_VERSION_POS) != 0) { --------^ cc: Warning: dgif_lib.c, line 252: In this statement, the referenced type of th\ e pointer value "(GifPixelType ...)0" is "unsigned char", which is not compatib\ le with "char". sp->RasterBits = (GifPixelType *)NULL; --------^ cc: Warning: dgif_lib.c, line 747: In this statement, the referenced type of th\ e pointer value "(GifPixelType ...)malloc(...)" is "unsigned char", which is no\ t compatible with "char". sp->RasterBits ----------------^ cc: Warning: dgif_lib.c, line 750: In this statement, the referenced type of th\ e pointer value "sp->RasterBits" is "char", which is not compatible with "unsig\ ned char". DGifGetLine(GifFile, sp->RasterBits, ImageSize); ----------------^ cc: Warning: dgif_lib.c, line 802: In this statement, the referenced type of th\ e pointer value "(GifByteType ...)malloc(...)" is "unsigned char", which is not\ compatible with "char". ep->Bytes = (GifByteType *)malloc(size); ----^ emacs.c had one more: cc -c -fast -std -Demacs -I. -DHAVE_CONFIG_H -std -I/usr/local/include -I/usr/\ dt/include emacs.c cc: Warning: emacs.c, line 2520: In this statement, the referenced type of the \ pointer value "newpath" is "unsigned char", which is not compatible with "const\ char". len = strlen (newpath); --------^ cmdloop.c had: cc: Warning: cmdloop.c, line 507: Non-void function "Fcommand_loop_1" does not \ contain a return statement. DEFUN ("command-loop-1", Fcommand_loop_1, 0, 0, 0, /* ^ That was it. Here is the config. Full build attached. XEmacs 21.0 "Erzgeberg" configured for `alphaev56-dec-osf4.0d'. Where should the build process find the source code? /home/oberman/utils/x$ What installation prefix should install use? /usr/local What operating system and machine description files should XEmacs use? `s/decosf4-0.h' and `m/alpha.h' What compiler should XEmacs be built with? cc -fast -std Should XEmacs use the GNU version of malloc? no (The GNU allocators don't work with this system configuration). Should XEmacs use the relocating allocator for buffers? yes What window system should XEmacs use? x11 Where do we find X Windows header files? /usr/dt/include Where do we find X Windows libraries? /usr/dt/lib Additional header files: /usr/local/include Runtime library search path: /usr/dt/lib Compiling in support for XAUTH. Compiling in support for XPM images. Compiling in support for PNG image handling. Compiling in support for (builtin) GIF image handling. Compiling in support for TIFF image handling. Compiling in support for Berkeley DB. Compiling in support for GNU DBM. Compiling in support for CDE. Compiling in support for ToolTalk. Compiling in EXPERIMENTAL support for Drag'n'Drop ( CDE ). Compiling in support for proper session-management. Using Lucid menubars. Using Lucid scrollbars. Using Motif dialog boxes. Compiling in DLL support. movemail will use "flock" for locking mail spool files. R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman(a)es.net Phone: +1 510 486-8634

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Re: [Success] 21.0 Danish Landrace on Solaris 2.6 / SunPro cc 26 years, 3 months

SL Baur

N J Doye <nic(a)niss.ac.uk> writes in xemacs-beta(a)xemacs.org: > Not sure what the --with-pop option is supposed to do, so I didn't > use it. It adds pop3 support to movemail. > However, I use POP to get my mail for VM. Apparently VM doesn't use movemail for pop3.

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Re: [success, after a while] 21.2 "Aether-pre3" XEmacs Lucid (beta2) on mips-sgi-irix6.3 26 years, 3 months

SL Baur

Remek Trzaska <remek(a)npac.syr.edu> writes in xemacs-beta(a)xemacs.org: > I had to edit src/dired.c to get rid of compiler errors. Do > `user_cache' variables have to be initialized at the end of the file?? It looks like a misapplied patch. > -static char **user_cache; > -static int user_cache_len; > -static int user_cache_max; > +static char **user_cache = NULL; > +static int user_cache_len = 0; > +static int user_cache_max = 0; This will cause crashes on many systems, don't try this at home kids. :-) 1998-08-19 SL Baur <steve(a)altair.xemacs.org> * dired.c (vars_of_dired): Fix misapplied patch. Index: src/dired.c =================================================================== RCS file: /usr/local/xemacs/xemacs-20.0/src/dired.c,v retrieving revision 1.18.2.1 diff -u -r1.18.2.1 dired.c --- src/dired.c 1998/08/11 21:57:50 1.18.2.1 +++ src/dired.c 1998/08/19 21:14:51 ＠＠ -935,8 +935,8 ＠＠ `file-name-all-completions'. */ ); Vcompletion_ignored_extensions = Qnil; -} user_cache = NULL; user_cache_len = 0; user_cache_max = 0; +}

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Re: Macros: Scheme vs Common Lisp 26 years, 3 months

Karl M. Hegbloom

I'm saving this thread to read after I've completed Part 4 of "Scheme and the Art of Programming", which discusses "Extending the Language", with macros and whathaveyou.

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socket connections on win95 26 years, 3 months

Roman Milner

I just built a binary of 21.0-b52 on nt and then transported it to a win95 machine. On the win95 box it hangs whenever it tries to make a socket connection. I know perl has a similar problem with sockets on 95 so I assume it's a 95 problem and not an xemacs problem. I'm wondering if anyone else has also seen this and knows a work around or if it also happens on 98. Thanks, ^Roman -- It's too bad that whole families have to be torn apart by something as simple as wild dogs. -- Deep Thoughts by Jack Handey ------------------ Roman Milner roman(a)speeder.com

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[script] `backup-cvs-work' 26 years, 3 months

Karl M. Hegbloom

Thought this might prove itself useful to yous. The first is from "/etc/cron.d", the second is a sample "CVS-backup-dir-list" file, and the third is the script itself. This has been updated a little since the last time I submitted it.

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XEmacs-Beta August 1998