an immense accumulation of commodities

Well, ilc07 was pretty fabulous. The setting and the weather was unfeasibly beautiful. (I found/find it interesting that a not insignificant number of people were compelled to invoke Harry Potter in response.) The organisation was great, and the papers and presentations of a pretty consistently high standard. My notes follow. They will make most sense to those who were there, I guess.

Day 1

MPS: Disappointingly too much reminiscing about dead projects. I didn’t mind the business anecdotes (although the frogs were unnecessary). The MPS system itself seems very interesting, but I felt we got only the merest glimpse.

Debugging: OK. Interesting that there seems little difference between a commercial lisp and something like SBCL. ll (low-level language, as opposed to LAP) seems an ideal target to which to compile C…

Day 2

Lisp: Themes and History: A presentation in two parts. The first a fascinating piece of lisp archeology. (LISP looked real ugly pre-parens.) The second a quick overview of semantically-preserving rewrite rules to compile lisp to a machine independent LAP. But why?

Constraint Propagation: Probably very good, but I didn’t understand why I should care. As Christophe Rhodes has already mentioned, a number of the talks lacked the slide on the motivation for the research/approach/product/technique.

Binary DSL in Dylan: Engaging presenters. Two takeaways: there is life in Dylan yet, and procedural macros rule.

FREEDIUS: Looked cool, but what is it for? (I wonder if it can track a ball in real time?)

ESA: I enjoyed it (: Very useful for when you need that instant gui gratification.

Ltk: Like ECLM’06 but with Tetris!

Gene Expressions: Very dynamic, but didn’t understand a word. Cyrus gets the prize for blatantly ignoring the timekeeper.

Teaching CS: Great presentation. I’ll never read LiSP the same way again.

R6RS: Nicely presented, but it really did make Scheme seem the amateur little brother of Common Lisp. Square brackets? Case sensitivity?

Next 700 Libraries: I found this fascinating, but it seems some people have missed the point: it is a message of great optimism to demonstrate that automated assistance in the conversion of existing, substantial, documented and test-enhanced Java libraries is feasible.

Day 3

CL-HTTP: A report from a piece of the lisp world which seems to have been becalmed for the last 10 to 15 years… Very odd.

SC: S-expression-based C. Excellent slides. Who knew the future of C was sexps?

Crosscuts: A nice presentation, not least for introducing me to “the tyranny of the dominant decomposition”.

Inter-domain Network Management: Key point: rewriting everything in Lisp was the only way of reducing the errors introduced by the C and Perl modules.

CL-SNA: Next year’s ECLM in Istanbul should be a blast.

DAUTI in Scheme: Using such standard Scheme facilities as structs and macros, it took the author three evenings to get this going. Why so long?

Classification: Bayes meets Shannon. Probability meets belief. Umm, OK.

LispWorks Demo: And here’s one I made earlier. Frankly, it didn’t make me jump out of my seat (or some other appropriate Simon Cowellism…)

Dynamic Memory Management: A highly accomplished presentation from someone who really understands both the subject and the state of the art. Impressive.

ALU meeting: I will pass over this except to say (i) Europe and the ALU seem to be going their separate ways, and (ii) Rusty, I voted for you!

Day 4

HOP: Highly professional presentation backed up by 2-300k lines of scheme code. Something to explore one day.

Racer OWL: Description Logics are different from Object Orientation. Or Ontological Orientation. Or something.

List Comprehensions: LOOP!

CLforJava: Might have been better to take his own advice and not explain CLOS and MOP to the group. (Geoff — what’s wrong with “close”?)

Google SoC Lunch: Everyone hates Kenny…

DADTs: I missed the beginning of this, so it rather passed me by.

XMLisp: AgentCubes is very pretty. Which can’t be a bad thing…

Extensible Sequences: Five implementations and counting. Christophe dealt nicely with some heckling from the pensioners’ seats.

Liskell: Sexps are good for what ails you; Haskell means not having to write tests; and some very cute examples.

Scalable Lisp Applications: Some of this was interesting, but I came away with an impression much like Luke Gorrie’s, I’m afraid. (Now there’s a smart guy.)

Of course, the really cool stuff happened outside the conference room. But that’s another story.

I am very much looking forward to ilc07 after a few almost lisp-free months (too much day-job). My only contact has been the invaluable Planet Lisp and the odd quick browse of the #lisp logs. Certainly seems to have been lots of McClim activity in my absence (perhaps I should stay away?) - I’m sure my half-finished apps will need some serious forward-porting. Or perhaps I’ll be converted to CAPI…

Predicted highlight: obviously ESA.

Possible break-out hit: CL-HTTP.

Most heat least light: …

See you there!

Following overwhelming^[*] demand, FTD, the Flexi Trivial Directory editor, is now a project on common-lisp.net.

FTD is now available via
darcs get http://common-lisp.net/project/ftd/darcs/ftd
or here.

Thanks to common-lisp.net mailing lists are at:

• ftd-devel for developers
• ftd-cvs CVS log feed.
• ftd-announce for announcements.

While FTD has a lot of dependencies, they are pretty common libraries^[†] and it would be nice to know if it built and was able to get a directory listing on your system. Feedback to the devel list, please (:

† I know, it’s that old ‘Common Lisp has too many libraries’ complaint…

What do you get when you put SBCL’s windows port (helpfully packaged by Nikodemus Siivola), EmacsW32, Slime, McClim and Xming on a USB stick?

A nice little portable development environment with cross-platform GUI, of course!

I resurrected FTD, the Flexi Trivial Dired, after some months’ hiatus. When I started the project last year it was to provide another ESA (Emacs Style Application) example, and to provide a test-bed for McCLIM application integration. Well, ESA was split out of Climacs anyway, and Clim Desktop made its appearance without a directory editor.

Still, it’s fun to see how much of the Emacs Dired functionality can be obtained by putting together a bunch of common lisp libraries. Documentation and downloading instructions can be found here.

Being an ESA, FTD inherits all of the cool help functionality built into the ESA framework. Unfortunately, ESA won’t write the documentation for you yet…

A couple of things makes FTD actually usable (from a UI point of view) in this revision. First, I remembered to specify :allow for the :end-of-line- and :end-of-page-actions. And, second, Troels Henriksen pointed out, after a few seconds of looking at the code, that I was using the default #'eql cache test, even though I was comparing cache-values of freshly consed lists each time through the display loop. Correcting this test (to :cache-test #'equal) prevented McClim from redrawing everything each time I moved the cursor…

Comments and patches welcome (splittist at splittist com). If there is any real interest I’ll set up a proper project.

In working on indenting LOOP forms for Climacs (see the latest update here) I’ve come across a couple of competing ideas on how they should be formatted.

From cl-indent-patches.el (”Original version by rst” with patches by “salem” and “bromley” according to the header) we have the following “validation” (line numbers added by me):

 1 (loop for i from 0 below 2
 2       for j from 0 below 2
 3       when foo
 4         do (fubar)
 5            (bar)
 6            (moo)
 7         and collect cash
 8               into honduras
 9       else do ;; this is the body of the first else
10               ;; the body is ...
11               (indented to the above comment)
12               (ZMACS gets this wrong)
13            and do this
14            and do that
15            and when foo
16                  do the-other
17                  and cry
18       when this-is-a-short-condition do
19         (body code of the when)
20       when here's something I used to botch do (here is a body)
21                                                (rest of body indented same)
22       do
23    (exdented loop body)
24    (I'm not sure I like this but it's compatible)
25       when funny-predicate do ;; Here's a comment
26                               (body filled to comment))

The forms at issue are the DOs at 9-12 (and 25-6; compare with 20-21), 18-19 and 22-24. I would indent these like this:

 9       else do ;; this is the body of the first else
10              ;; the body is ...
11              (indented to the above comment)
12              (ZMACS gets this wrong)

(I see no reason for conforming to a dubious commenting style. But I’m interested to know why not doing so is “wrong”.)

18       when this-is-a-short-condition do
19                                        (body code of the when)

(I see no reason to special-case a “short-condition”, whatever that is.)

22       do
23         (exdented loop body)
24         (I'm not sure I like this but it's compatible)

(Exdenting is just gross - but “compatible” with what?)

Of course, I’m now doubting my own taste, so I’d be interested in what the Planet Lisp community thinks. Answers in the comments for summarising in a later edition…

Climacs has a bunch of search commands, but it needs more!

What it has at the moment are many of the standard ones:

• Incremental Search (forward and back) - C-s and C-r
• String Search (and Reverse String Search)
• Word Search (and Reverse Word Search)
• Regex Search Forward and Regex Search Backward
• How Many (lines after point match some regex)
• Replace String (unconditionally)
• Query Replace - M-%

and a few less common:

• Multiple Query Replace
• Query Exchange
• Multiple Query Replace From Buffer

Incremental Search and Query Replace have a fair subset of the GNU emacs functionality in their loops. While in an incremental search you can switch direction, add a newline to the search string (C-j), snarf the next word into the search string (C-w), or the remainder of the line (C-y), or the top of the kill ring (M-y) etc. While in a query replace loop you can replace, skip, exit, replace and exit, or just replace the rest of the matches.

So far so good for the normal stuff. You’ll see that some functionality isn’t there yet. Partially this is just that no-one has gotten around to it (and if your favourite functionality is missing patches are appreciated!). But partially this is because climacs isn’t emacs, and we’re still feeling our way towards what is the best way to use the command-loop, in which a lot of CLIMy magic happens.

As an example of the issues, take the emacsly-traditional way of invoking a string search - C-s immediately followed by the command to exit the search (RET in GNU emacs, Altmode in TWENEX EMACS, etc). The Incremental Search command works by setting up a special command table (a CLIM object imaginatively named isearch-climacs-table) that maps gestures to commands (so that, for instance, C-j is mapped to com-isearch-append-newline). The gesture #\Newline invokes com-isearch-exit. But when the search string is empty, #\Newline should run the command String Search (or Reverse String Search, if we’re isearching backward). String Search prompts the user for a string to search for (!), and one of the beauties of CLIM is that the system handles this automatically. But not here, where we are inside another command (and, indeed, inside another command loop - but that’s another story), so for the moment I have to reach behind the curtain and pull a few levers myself:

(execute-frame-command *application-frame*
                       (funcall
                        *partial-command-parser*
                        (frame-command-table *application-frame*)
                        (frame-standard-input *application-frame*)
                        (if search-forward-p
                            `(com-string-search ,*unsupplied-argument-marker*)
                            `(com-reverse-string-search ,*unsupplied-argument-marker*))
                        0))

Obviously this is uglyrific, but the moral of the story isn’t that CLIM makes normal things hard (although there are some things about command tables that the CLIM 2 spec leaves rather underspecified), but that I don’t yet know the best way to get this (admittedly rather special) behaviour out of the existing command loop. (One possibility: have a pending-commands slot that the command-loop checks, analogous to the remaining-keys slot used by the keyboard macro machinery.)

Another thing I don’t understand is why GNU emacs doesn’t have a command like Multiple Query Replace. This prompts for pairs of strings and then goes through the buffer asking if you want to replace any of the first strings of the pairs with the corresponding second string. Since this happens essentially in parallel, you can replace FOO with BAR, BAR with BAZ, BAZ with QUUX and QUUX with FOO in one invocation, without any messing around with temporary strings or abbrevs (as suggested as workarounds in the GNU emacs documentation). (The command Query Exchange is specialised for the case when you want to swap each FOO with a BAR and vice versa.) If you think entering the search and replacement strings in the minibuffer is prone to mistake, you can put them in a buffer and use Multiple Query Replace From Buffer. An essential refactoring tool, I would have thought.

Well, essential once climacs gets Tag Files (the Zmacs name for a collection of buffers or files, whether named in a TAG file, or all the open buffers, or all the files in a system etc.). Then various searching commands can be run over all the files in a Tag File. Which means the ability to suspend and resume a given search, and to visualise pending operations, becomes important.

And then there are the syntax specific searches that climacs should really have - things that allow you to ask for all lists of length 3 with CL:IF as the first element…

But all that is for another day.

Climacs has quite a few help commands now. The picture above shows Apropos Command (in the lower panel) and Describe Command (in the upper panel).

The interesting thing is that the upper panel was obtained by clicking on the “Kill Line” heading below. And the magic involved?

(present command
         `(command-name :command-table ,command-table)
         :stream out-stream)

when printing and

(define-presentation-to-command-translator describe-command
    (command-name com-describe-command help-table
                  :gesture :select
                  :documentation "Describe command")
    (object)
    (list object))

to make it clickable.

Which just goes to show some of the cool things you get for free if you use CLIM.

The full list of help commands currently available is:

• Apropos Command (C-h a)
• Describe Bindings (C-h b)
• Describe Key Briefly (C-h c)
• Describe Command (C-h f)
• Describe Key (C-h k)
• Where Is (C-h w)

In fact, all these commands are part of ESA, and should therefore be available to any Emacs Style Application written using that framework.

ECLM 2006 was my first Lisp event. In fact, it was my first programming event. I had a great time.

As the other blogging attendees have noted, the presentations were of varying interest. The AllegroGraph presentation was a bit once-over lightly, and never touched upon telecom fraud detection (unless that’s what Osama Bin Laden was wanted for). In contrast to many others I found James Anderson’s talk quite interesting, if only for the “here’s something interesting and perhaps counter-intuitive we found when implementing the system” moments. Arthur Lemmens, Martin Cracauer and David McClain all went for a low key presentation style, which worked with their material and the crowd. But David McClain’s late-night-DJ voice, impressive pictures and fascinating background stole the show.

The most common question in the breaks, asked with the expectation of a negative answer, was “Do you use lisp in your work?”. The negative answer was, of course, forthcoming in the vast majority of cases.

It was fun putting faces to nicks. Andreas Fuchs managed to look nothing at all like antifuchs, for some reason I can’t articulate. Whereas Juho Snellman did look like jsnell. (Christophe Rhodes is never Xophian, because the fangs barely show IRL…).

Many thanks to Edi and Arthur!