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Do symbols need to be EQ?
by Edi Weitz 16 Aug '15

16 Aug '15

Just out of curiosity and without any relevance in practise: Is there one place in the standard where it is explicitly said that two symbols which are the "same" symbol must be "identical"? I know that there are a couple of examples where this is implied, but formally the examples aren't part of the standard, right? The EQ dictionary entry for example shows this example: (eq 'a 'a) => true and then it continues with this note (emphasis mine): "Symbols that print the same USUALLY are EQ to each other because of the use of the INTERN function." And the entry for INTERN is actually the closest I could find in terms of clarification because it says that if a symbol of a specified name is already accessible, _IT_ is returned -- which sounds like object identity to me. But how does this fit into the picture? CL-USER 1 > (defparameter *s* 'foo) *S* CL-USER 2 > (unintern 'foo) T CL-USER 3 > (defparameter *s2* 'foo) *S2* CL-USER 4 > (eq *s* *s2*) NIL *S* has lost its home package and is thus not EQ to *S2*, sure, but how do we explain this in terms of object identity? Has the UNINTERN operation changed the identity of *S* which once was the one and only CL-USER::FOO but can't be anymore because this role is now occupied by *S2*? Did I miss some clarifying words in the standard? Did I just manage to confuse myself? Thanks, Edi. PS: The UNINTERN entry warns about side effects which could harm consistency, so maybe this is what they meant?

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Proper behavior of slot-initforms in defstruct?
by Jean-Claude Beaudoin 04 Aug '15

04 Aug '15

Please consider the following code: (defparameter init-a 1) (let ((init-a 42) (serial-no 0)) (defstruct foo (a init-a) (b (incf serial-no))) (defun get-foo-serial-no () serial-no)) (defstruct (bar (:include foo)) (c 33) d) When one loads the above and then try to call #'make-bar the result varies widely from one lisp implementation (clisp) to another. clisp: (make-bar) --> #S(BAR :A 1 :B 1 :C 33 :D NIL) ccl: (make-bar) --> <enter the debugger saying: "Unbound variable: SERIAL-NO"> lispworks, allegro and sbcl also behave more or less like ccl. What is the proper ANSI-CL behavior in this case here? Is clisp right in evaluating the slot initform in its "proper" lexical context? Or is the correct behavior to replicate the slot initform verbatim in the sub-structure constructor regardless of its original lexical context like the others do? I guess that this question has probably been asked before, in a somewhat distant past, but my google skills have not been sharp enough to find it, sorry.

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Caching of effective methods in custom method combinations
by Edi Weitz 21 Jul '15

21 Jul '15

Hi everybody, Here's some behavior I see on SBCL as well as LispWorks, so I'm assuming for now they're right in doing so. My question would be why they are. I start with the following code which I compile and load: ;;;;;;;;;;;;;;;;;;;;;;;; (defvar *current-qualifiers* '(:a :b :c)) (define-method-combination test () ((methods *)) (let ((selected-methods (loop for method in methods when (intersection (method-qualifiers method) *current-qualifiers*) collect method))) `(call-method ,(first selected-methods) ,(rest selected-methods)))) (defgeneric foo (thing) (:method-combination test)) (defmethod foo :a (thing) '(:red)) (defmethod foo :b (thing) '(:blue)) ;;;;;;;;;;;;;;;;;;;;;;;;;; Now, in the REPL I do the following: CL-USER> (foo 42) (:BLUE) CL-USER> (setq *current-qualifiers* '(:a :c)) (:A :C) CL-USER> (foo 42) (:BLUE) I almost expected this. The effective method obviously isn't computed anew but was cached. But even if I now re-evaluate the DEFINE-METHOD-COMBINATION form, (FOO 42) will still return (:BLUE). Only if I re-evaluate the DEFGENERIC form will the return value change to (:RED). My question is if the standard somewhere allows this caching to happen. That would for example mean that any kind of "dynamic method combination" (for example based on the time of the day, just for grins) is impossible. Or am I missing something and my interpretation is wrong? Thanks, Edi.

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Should GC hooks be used to help broken software?
by Elias Mårtenson 06 Jul '15

06 Jul '15

The following question was raised during my development of an asynchronous library <https://github.com/lokedhs/cl-rabbit-async> I'm currently building for RabbitMQ. In summary, the library allows you to create an object of type ASYNCH-CONNECTION, from which instances of ASYNC-CHANNEL can be retrieved. A connection holds a reference to all channels that it uses, and each channel holds a reference to its connection. The connection object has a pointer to a native CFFI object that for the underlying connection (my library is built on the RabbitMQ C API). My question is: Should I use trivial-garbage to create a GC hook for the connection object so that if the user of the library forgets to close the connection, it will get closed eventually once it's GC'ed? I can see arguments for both behaviours: - It's a bad idea, since losing the reference to the connection object means that the program is broken, and silently cleaning up the underlying connection might hide the fact there is a bug (if the GC doesn't run often enough I might have hundreds or even thousands of lingering connections) - On the other hand, it might be a good idea since Lisp developers often use the REPL to experiment, so it's easy to accidentally lose a reference to an object during testing. Thus, using the GC hook will improve the stability of one's development environment. To me, there is no strictly correct answer to the question, which is why I'm asking for suggestions from you guys. Regards, Elias (loke on #lisp)

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cl-ppcre:split question
by Mark H. David 02 Jul '15

02 Jul '15

The examples for cl-ppcre:split here http://weitz.de/cl-ppcre/#split include this tempting recipe: (split "\\s+" "foo bar baz frob") => ("foo" "bar" "baz" "frob") However, (split "\\s+" " foo bar baz frob") => ("" "foo" "bar" "baz" "frob") I.e., the result list includes an empty string as the first element if there are one or more whitespace characters at the beginning of the string. How can I get rid of the empty string at the beginning? Is there a regexp match for this that would work with split? Thanks, Mark

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Heads up on Graphics Ports
by David McClain 08 May '15

08 May '15

Hi all, I just ran into a glitch in the new LW7 for Mac and Windows. Starting some time ago, there is an additional parameter in GRAPHICS-STATE called SCALE-THICKNESS. Up to now, it had defaulted to NIL, and that’s why i never noticed when it was introduced. Starting in LWM7.0 and LWW7.0 it defaults to T. Not sure when scaling thickness to transformed coordinates would make sense. I have scaled things in the past according to zoom state: if you double the window pane size, then thicknesses of lines also doubles in my plotting package. I’m hard pressed to imagine a situation in which I’d ever want line thickness to scale according to the affine transform in effect. And how would that work, when the domain covers (-1 1) while a range covers (10 1000)? At any rate, just a heads up to everyone. Not broken, just different in the new version of LW. 73 de Dave, N7AIG David McClain N7AIG(a)arrl.net

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[CfPart] ELS 2015, April 20-21 2015, London
by Didier Verna 01 Apr '15

01 Apr '15

ELS'15 - 8th European Lisp Symposium Goldsmiths College, London, UK April 20-21, 2015 http://www.european-lisp-symposium.org/ Sponsored by EPITA, Goldsmiths University of London, Franz Inc., Lispworks Ltd., Clozure Associates and Google Recent news: - A few seats left, still time to register! - Programme now online (schedule may still change a little) - Invited speakers announced: Zach Beane, Bodil Stokke, Martin Cracauer The purpose of the European Lisp Symposium is to provide a forum for the discussion and dissemination of all aspects of design, implementation and application of any of the Lisp and Lisp-inspired dialects, including Common Lisp, Scheme, Emacs Lisp, AutoLisp, ISLISP, Dylan, Clojure, ACL2, ECMAScript, Racket, SKILL, Hop and so on. We encourage everyone interested in Lisp to participate. The 8th European Lisp Symposium features 3 invited talks, one tutorial, 4 technical sessions and 2 lightning talks slots. The full programme is now available on the website: http://www.european-lisp-symposium.org/. Programme chair: Julian Padget, University of Bath, UK Local chair: Christophe Rhodes, Goldsmiths, University of London, UK Programme committee: Sacha Chua — Toronto, Canada Edmund Weitz — University of Applied Scicences, Hamburg, Germany Rainer Joswig — Hamburg, Germany Henry Lieberman — MIT, USA Matthew Flatt — University of Utah, USA Christian Queinnec — University Pierre et Marie Curie, Paris 6, France Giuseppe Attardi — University of Pisa, Italy Marc Feeley — University of Montreal, Canada Stephen Eglen — University of Cambridge, UK Robert Strandh — University of Bordeaux, France Nick Levine — RavenPack, Spain Search Keywords: #els2015, ELS 2015, ELS '15, European Lisp Symposium 2015, European Lisp Symposium '15, 8th ELS, 8th European Lisp Symposium, European Lisp Conference 2015, European Lisp Conference '15 -- My new Jazz CD entitled "Roots and Leaves" is out! Check it out: http://didierverna.com/records/roots-and-leaves.php Lisp, Jazz, Aïkido: http://www.didierverna.info

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[pro] Default safety level and specialized arrays
by Edi Weitz 12 Mar '15

12 Mar '15

Hi everybody, After rummaging around in the HyperSpec and various implementation manuals I came to the following conclusion: 1. The standard doesn't prescribe such thing as a default safety level for CL implementations and there's no portable way to figure out the safety level of the global environment. (And the same holds for other optimize qualities.) The closest I could find in the CLHS is 3.3.1 where they talk about an "implementation that always processes code as if safety were high." From this I conclude that implementations are allowed NOT to do this or otherwise there would be no need to mention it. The LispWorks manual for example describes the defaults in section 9.5 about compiler control, but for SBCL I couldn't find them in the manual. 2. The standard doesn't prescribe what should happen if you try to write an element of a wrong type to a specialized array, even in safe code. Both LispWorks and SBCL will by default complain in this case but my understanding is that you can't rely on this in portable code. So, my question is whether the above is correct or if I missed something? Thanks, Edi.

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[pro] RavenPack Lisp Job
by Andrew Lawson 23 Feb '15

23 Feb '15

Good afternoon all We at RavenPack in Marbella, Spain, are searching for a Common Lisp developer. The webpage linked below goes into more detail. I'd like to encourage anyone with an interest to have a look. We are a growing company with an expanding development group and offer the opportunity to work with interesting technologies and a great group of people. Applicants must already be able to work legally in the E.U. The job is situated in our Marbella office, no remote work is available. We are looking for someone interested in building a career with us, not a short-term contractor. http://www.ravenpack.com/company/careers/ Andrew -- Andrew Lawson Lisp Development Manager RavenPack International S.L. alawson(a)ravenpack.com

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[pro] [Final CfP] ELS 2015 submission deadline extended to March 1st
by Didier Verna 22 Feb '15

22 Feb '15

ELS'15 - 8th European Lisp Symposium Goldsmiths College, London, UK April 20-21, 2015 http://www.european-lisp-symposium.org/ Sponsored by EPITA, Franz Inc. and Lispworks Ltd. Recent news: - *** Submission deadline extended to March 1st *** - Invited speakers announced: Zach Beane, Bodil Stokke, Martin Cracauer - Registration to open early March The purpose of the European Lisp Symposium is to provide a forum for the discussion and dissemination of all aspects of design, implementation and application of any of the Lisp and Lisp-inspired dialects, including Common Lisp, Scheme, Emacs Lisp, AutoLisp, ISLISP, Dylan, Clojure, ACL2, ECMAScript, Racket, SKILL, Hop and so on. We encourage everyone interested in Lisp to participate. The 8th European Lisp Symposium invites high quality papers about novel research results, insights and lessons learned from practical applications and educational perspectives. We also encourage submissions about known ideas as long as they are presented in a new setting and/or in a highly elegant way. Topics include but are not limited to: - Context-, aspect-, domain-oriented and generative programming - Macro-, reflective-, meta- and/or rule-based development approaches - Language design and implementation - Language integration, inter-operation and deployment - Development methodologies, support and environments - Educational approaches and perspectives - Experience reports and case studies We invite submissions in the following forms: Papers: Technical papers of up to 8 pages that describe original results or explain known ideas in new and elegant ways. Demonstrations: Abstracts of up to 2 pages for demonstrations of tools, libraries, and applications. Tutorials: Abstracts of up to 4 pages for in-depth presentations about topics of special interest for at least 90 minutes and up to 180 minutes. The symposium will also provide slots for lightning talks, to be registered on-site every day. All submissions should be formatted following the ACM SIGS guidelines and include ACM classification categories and terms. For more information on the submission guidelines and the ACM keywords, see: http://www.acm.org/sigs/publications/proceedings-templates and http://www.acm.org/about/class/1998. Important dates: - 01 Mar 2015: Submission deadline *** EXTENDED *** - 15 Mar 2015: Notification of acceptance - 29 Mar 2015: Early registration deadline - 05 Apr 2015: Final papers - 20-21 Apr 2015: Symposium Programme chair: Julian Padget, University of Bath, UK Local chair: Christophe Rhodes, Goldsmiths, University of London, UK Programme committee: Sacha Chua — Toronto, Canada Edmund Weitz — University of Applied Scicences, Hamburg, Germany Rainer Joswig — Hamburg, Germany Henry Lieberman — MIT, USA Matthew Flatt — University of Utah, USA Christian Queinnec — University Pierre et Marie Curie, Paris 6, France Giuseppe Attardi — University of Pisa, Italy Marc Feeley — University of Montreal, Canada Stephen Eglen — University of Cambridge, UK Robert Strandh — University of Bordeaux, France Nick Levine — RavenPack, Spain Search Keywords: #els2015, ELS 2015, ELS '15, European Lisp Symposium 2015, European Lisp Symposium '15, 8th ELS, 8th European Lisp Symposium, European Lisp Conference 2015, European Lisp Conference '15 -- My new Jazz CD entitled "Roots and Leaves" is out! Check it out: http://didierverna.com/records/roots-and-leaves.php Lisp, Jazz, Aïkido: http://www.didierverna.info

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