Kevin Reid's blog

There seems to be a recurring misconception about writing .asd files. It is not necessary to start your asd with (defpackage :foo.system ...) (in-package :foo.system) to “avoid polluting the package asdf loads your system in”.

Every time an .asd file is loaded, ASDF creates a fresh package to load it in. The relevant code from ASDF is:

(defun make-temporary-package ()
  (flet ((try (counter)
           (ignore-errors
                   (make-package (format nil "ASDF~D" counter)
                                 :use '(:cl :asdf)))))
    (do* ((counter 0 (+ counter 1))
          (package (try counter) (try counter)))
         (package package))))

(defun find-system (...)
  ...
      (let ((package (make-temporary-package)))
        (unwind-protect
             (let ((*package* package))
               ...
               (load on-disk))
          (delete-package package)))
  ...)

So, whenever you load an asd file, the package is fresh and :uses CL and ASDF.

There are reasons to define a package for your asdf system definition.

• If you are creating any classes, such as custom ASDF component types, then, since classes are not garbage collected (MOP specifies that the list of a class's subclasses can be retrieved, and no implementation I know of uses weak references for the purpose), naming them with symbols in a consistent package (rather than the asdf temporary package) ensures that reloading the system definition does not create useless additional copies of the classes.
• If you are defining functions or other named entities in your system definition (which should of course only be done if they are also necessary to load the system) and want to be able to refer to them, such as for debugging, with nice interned symbol names.
• If you want to be able to (load "foo.asd") rather than going through asdf:find-system.

The disadvantages I can think of for defining a package for your system definitions are that the package list becomes more cluttered (only noticeably if for some strange reason you're loading many system definitions and not loading the defined systems), you're using more of the global package namespace (probably not a significant concern if you use a naming scheme like foo and foo.system), and your code is marginally more complex.

So there are good reasons for (and maybe some against) defpackage in your asd, but package hygiene is not one of them.

[Edited 2009-11-26 to be less worded against defpackage after consideration and feedback.]

You probably already know about this if you're interested, but SparkFun Electronics will be having, on January 7, a “Free Day” on which you can order up to $100 and pay only shipping (plus any amount over $100). Shipping, to my location by the cheap options, was shown as ~$10 (thus “91% off”, not considering tax).

(I have no affiliation with, and have not ordered anything from, SparkFun Electronics; this is just some info that showed up in my feed reader. As far as I’ve heard they’re good folks.)

SparkFun’s product line is somewhat oriented towards the hip electronics hobbyist, the sort of stuff that Make talks about: Arduino, text and graphic LCDs, blinky light kits, wireless stuff (serial links, GPS, Bluetooth), robots, sensors, breakout boards/modules for surface mount components. Many of these items are high priced, but they have notable cheap stuff too; when I heard about this sale yesterday my first-cut list of 11 interesting items only totaled $62.

I was working on some automated document generation, building the process, revising the input document, and checking the results, and got tired enough of typing "make output/foo.txt && open output/foo.txt" and then going back and editing that line when I wanted to check the PDF version etc. that I wrote a tool which I hope will have more general application as well. I called it “maken”:

#!/bin/sh
# Make files and view the results.
make "$@" && open "$@"

Or it could be generalized into being a combinator, running any two commands, rather than just make and open, specified as the first two arguments:

#!/bin/sh
ca="$1"
shift
cb="$1"
shift
"$ca" "$@" && "$cb" "$@"

(Which, for the Haskell folks, should be called &&&, except that that would be annoying to enter in the shell.)

I'm on Google Wave (by way of my participation in GSoC 2009). Tell me what's worth my time to do with it.

My ID is apparently kpreid.switchb.org@googlewave.com. (kpreid was taken, hmph.)

I blame a certain English teacher last year for introducing “FAIL” into my vocabulary.

Every time you write “ | ” in shell, that's concurrent programming.

\documentclass{article}
\usepackage{verbatim}
\begin{document}
  \verbatiminput{\jobname.tex}
\end{document}

What do practicing Java programmers call the part of a method definition that isn't the { body }?

__________/ this bit here \___________
public static void main(String[] args) {
  // not this part
}

A quick search turned up the Java Language Specification, Second Edition calling it a MethodHeader in the grammar, but it doesn't use that term in the text and I want to know what term(s) are used in practice, not solely by language lawyers.

(“Signature” is not correct, as that includes only the method name and parameter types, not modifiers and result type.)

Both of the non-internet-based computer-related classes I'm taking this semester are (only offered as) once-per-week night classes, nominally ending at 9:30. So I'm talking with someone after class — — gee, it's bedtime already.

Late update on Caja-CapTP:

Google Summer of Code is over. I passed based on revised goals, but I'm not happy with the state of the code and I did not complete any significant part of the original plan.

Regarding the items mentioned in my last update:

• Write more documentation/comments.
• Commit as much of the work-in-progress as I can.
  • ...including the incomplete CapTPConnection, even though its tests don't pass yet, so that the partial work can be counted.

I committed CapTPConnection, and found and fixed enough infrastructure (whenResolved, CommTable, SwissTable, deSubgraphKit, etc.) bugs that it starts up and can do a basic operation or two. It's not useful for anything, but it's a lot closer to running than it was at the time of my last update.

Also, I removed dependencies on 'window' so in principle it will operate on a non-browser (server) JavaScript implementation. This has not been exercised because there is no browserless driver for the test scripts yet.

I stated that I would continue working on Caja-CapTP past the GSoC work period; however, with the time occupied by schoolwork, I have not had time or brain space to do so yet. I am not going to abandon the project.

Java programming class (yes, I know Java already) today, introducing loops. Task: write a factorial program. I wrote mine to use int arithmetic if possible, floating-point if not. Test the edge cases, of course. It says:

500! ≈ Infinity

I'm glad I used the “approximately equals” sign.

As I wrote before, I am currently attending MVCC, a two-year college, and need to choose a college to transfer to (for a bachelor’s in computer science).

So, tell me what college(s) I ought to consider.

(I have of course also heard the advice that it doesn’t matter that much, but I've got to choose from some short-list...)

I am willing to consider any location in the contiguous US, but have been looking mostly at New York choices as a way to make the research list manageably short.

I am not looking for vocational training; I can learn this year’s or last year’s hot technologies just fine by myself, thank you. I’m looking for general education (“well-rounding”, shall we say), useful theory, and practice in thinking. I wish to avoid a high-pressure or competitive academic environment. Also, at MVCC, I have greatly appreciated the instructors’ approachability, availability, and even willingness to acknowledge mistakes.

Outside of education, I am particularly interested in there being social opportunities for the socially awkward; chances to talk to like-minded people (i.e. total geeks), and opportunities to talk to unlike-minded people (for the practice!).

Please give me your recommendations. Just a name, your personal experience, comments on others’ recommendations, whatever info you’d like to share.

(On the other hand entirely, I’d also consider going directly from MVCC to a full-time job given the right opportunity. This will be the topic of an upcoming post.)

I've been having a lot of thoughts lately I'd like to publish, but seem a little bit too short for A Blog Post. Some options

1. Considered signing up for Twitter. Pro: short stuff is expected there; participating in the hot new thing; people interested in short-form will be on twitter and using the follow feature. Con: Reliability problems; YA thing to manage credentials and backup for; no hyperlinks; my favorite username is taken.
2. I could post stuff here. Particularly, LJ supports titleless posts.
3. I could use some other site, or build my own publishing system. [er, why?]

On reflection, I'm thinking to just post the stuff here and not have yet-another-distinct-place/site.

Readers, what would you prefer?

(This post is tagged “lisp” solely so that Planet Lisp will pick it up.)

Stuff done:

• Implemented generic literals.
• Implemented cyclic references in Data-E.
• Various cleanup, debugging support, and committing of stuff previously written.
• Wrote a wiki page documenting Caja-CapTP's major components and files.

Stuff to do:

• Write more documentation/comments.
• Commit as much of the work-in-progress as I can.
  • ...including the incomplete CapTPConnection, even though its tests don't pass yet, so that the partial work can be counted.

A while ago I got the idea to write a “my experiences with JavaScript” post; unfortunately, I’ve forgotten what I was going to put in it. However, yesterday someone said approximately “I need to learn JavaScript in 3 hours, what should I know?”, and I thought of quite a few not-immediately-obvious things to point out.

Had a bit of a breakthrough in debugging facilities: realizing that there's no reason I shouldn't modify my local copy of the Cajita runtime to provide more debug information (and it doesn't matter if it subtly breaks security, even, as long as Caja-CapTP is still compatible with the proper version).

Only a week or so left. I've discussed the matter with MarkM, and he pointed out (again) that I should work toward having useful-to-other-people components even if I haven't finished the one I intended to do.

Toward this end, I am going to work on Data-E (which is already part of the Caja-CapTP project) as a standalone serialization utility (for network and disk) as I understand it will be useful for Shakhar.

Todo items:

• Implement generic literals (description) to make it more JavaScript-natural.
• Implement cyclic object graph handling using Ref promise implementation already done.
• Commit all in-progress work as reasonable changesets (even the tests that don't yet pass).
• Document what works, design decisions, etc.
• Continue to work on CapTP itself as time permits.

I intend to continue working on the Caja-CapTP project beyond GSoC; both simply because it is a project of mine, and to mitigate my failure to complete the planned work on schedule. However, for the next few months it will have to compete with my college work rather than my procrastination.

Rosetta Code is a wiki where a variety of programming problems and language features are demonstrated in many languages, allowing language learning and comparison of features and paradigms.

If you'd like to contribute Common Lisp code to the project, I've just completed a classification of tasks in CL (like my prior one for E), so that it's easy to find the kind of problem one wants to work on at the moment.

One thing I find interesting about working on Rosetta Code is that many tasks bring with them some particular perspective — someone's notion of how programming necessarily works — and it can be a challenge to figure out the analogous way, or best way, to do it in your language is, and then explain it.

I'm having severe getting-around-to-actually-doing-the-work problems; I am far behind schedule. I think the problem is framing this as “work” rather than just another of the projects that I've found interesting and tinkered with. (I also blame Team Fortress 2 and Rosetta Code for providing attractive distractions...)

I've ported the “Ref” facility from E; this is necessary as CapTP is built on Ref semantics (promises, proxies, broken refs). I hope to very soon get the actual CapTP connection module up, then (as I wrote before) “define, document and implement a CapTP-over-HTTP protocol”.

(I previously mentioned implementing the Surgeon (serialization tool) but I then remembered that that's actually irrelevant to CapTP.)

Also: working without Internet access removes a whole lot of potential distractions — and one’s access to online documentation. Luckily I had some source code around which provided examples.

Common Lisp provides compile-file whose purposes is to convert a CL source file into an (implementation-defined) format which usually has precompiled code and is designed for faster loading into a lisp system.

compile-file takes the pathname of a textual lisp source file. But what if you want to compile some Lisp code that's not in a file already, perhaps because you translated/compiled it from some not-amenable-to-the-Lisp-reader input syntax, or because it contains unREADable literals? You can use a "universal Lisp file", which I know two ways to create (use whichever you find cleaner):

(cl:in-package :mypackage)
#.mypackage::*program*

(cl:in-package :mypackage)
(macrolet ((it () *program*))
  (it))

Suppose this is in "universal.lisp". Then to use it:

(defvar *program*)

(defun compile-to-file (form output-file)
  (let ((*program* form))
    (compile-file #p"universal.lisp"
                  :output-file output-file)))

This is just a minimal example; you'll also want to appropriately handle the return value from compile-file, provide an appropriate pathname to the universal file, etc. For example, here's an excerpt of the relevant code from E-on-CL, where I have used this technique to compile non-CL sources (emakers) into fasls:

(defparameter +the-asdf-system+ (asdf:find-system :e-on-cl))
(defvar *efasl-program*)
(defvar *efasl-result*)
...
(defun compile-e-to-file (expr output-file fqn-prefix opt-scope)
  ...
  (let* (...
         (*efasl-program*
           `(setf *efasl-result*
                  (lambda (...) ...))))
    (multiple-value-bind (truename warnings-p failure-p)
        (compile-file (merge-pathnames
                        #p"lisp/universal.lisp"
                        (asdf:component-pathname +the-asdf-system+))
                      :output-file output-file
                      :verbose nil
                      :print nil)
      (declare (ignore truename warnings-p))
      (assert (not failure-p) () "Compilation for ~A failed." output-file))))

(defun load-compiled-e (file env)
  (let ((*efasl-result* nil)
        ...)
    (load file :verbose nil :print nil)
    (funcall *efasl-result* env)))

Note that the pathname is computed relative to the ASDF system containing the universal file; also note the use of a variable *efasl-result* to simulate a "return value" from the compiled file, and the use of a lambda to provide a nonempty lexical environment, both of which are features not directly provided by the CL compiled file facility.

I have moved my web site to a new location: http://switchb.org/kpreid/.

I have done this because Apple has announced they are shutting down homepage.mac.com. While they offer a replacement, I do not want to have to change my URLs ever again, so I bought a domain name.

As well as moving the files I have updated my picture, changed some of the URL layout, updated some miscellaneous information, added an “About me” section for the front page, and fixed broken external links. Please let me know if I missed anything...

or even just critique it without respect to what's new.