Category: Link

Warp Speed Introduction to CLOS

[The Warp Speed Introduction to CLOS] is an extremely short overview of the Common Lisp Object System (CLOS). Newcomers to CLOS are often intimidated by its apparent complexity and possibly confused by its unusual approach. For a long time I considered CLOS to be “too hairy”, but after working on a large project that made heavy use of CLOS, I found that CLOS is actually one of the simplest and easiest object systems to understand and use. The more complex parts of CLOS can be safely ignored.

(via jrm)

How to handle large data in DrScheme

In the PLT discussion list thread titled “How to handle large data”, Kenichi wanted to load a very large file into DrScheme, 120,000 lines long, and it was hanging. Noel explained that because of debugging and performance instrumentation, DrScheme adds a lot of overhead, and that MzScheme could load the file just fine. Eli explained that DrScheme’s overhead could be made much smaller by making the contents of that file one big piece of quoted data, and that the overhead could be completely eliminated by putting the data in a file and then loading it.
The following code is a generalization of the two approaches that he described there, which were tailored to Japanese postal data.

(define info-list-data
  '(("Alpha" "Bravo" 1)
    ("Delta" "Echo" 2)))
(define-struct info (fname lname budget))
(define (info-data->info entry)
  (make-info (first entry) (second entry) (third entry)))
(define info-list
  (map info-data->info info-list-data))
(define info-list-from-file
  (map info-data->info
       (call-with-input-file "data-overhead-elimination.data" read)))
(display "Total budget: ")
(display (apply + (map (λ (info) (info-budget info)) info-list-from-file)))
(newline)

All Scheme Search

All Scheme Search is a Google based search engine for “Everything about the Scheme Programming Language”.
If seven pages of search results for “keyword arguments” is any measure, this looks pretty interesting :).
Addendum: 01/05/08
Here are two more: Scheme from the Florida Keys (actively updated) and Search PLT Scheme (not actively updated).

SCIgen – An Automatic CS Paper Generator

SCIgen is a program that generates random Computer Science research papers, including graphs, figures, and citations. It uses a hand-written context-free grammar to form all elements of the papers. Our aim here is to maximize amusement, rather than coherence.
One useful purpose for such a program is to auto-generate submissions to conferences that you suspect might have very low submission standards.

There are seemingly a number fun things that you could do with this!

Is Unicode in the code taboo?

MzScheme supports UTF-8 encoded files. Combine that with DrScheme, which makes it pretty easy to type in Unicode symbols, and somewhat suddenly, and surprisingly, you have the opportunity to work with symbols in your code beyond the standard 95 character ASCII set that we all know and love. What are the implications to you as a programmer?
The simplest implication is that you now have the ability to work with 100,000+ characters. In case you felt limited by the inability to use the characters of your native tongue like Tamil or perhaps Braille, you are restricted no more. Scientific programmers may enjoy using Greek letters; and who of us wouldn’t like to use the letter π to represent Pi? For Schemers, perhaps you would use → rather than ->.
The common theme among these atypical examples is that they facilitate communication. Without getting into the deep theories and concepts behind the value of communication and how the limitations of a language affect it; I would share a quote relevant to us as programmers regarding how we communicate to each other with our code:

Let us change our traditional attitude to the construction of programs: Instead of imagining that our main task is to instruct a computer what to do, let us concentrate rather on explaining to human beings what we want a computer to do.

— Donald Knuth
It seems like Unicode might facilitate that communication, but Unicode in code today is not at all common. Why might that be?
The usual suspects are that our tooling (IDEs and text-processing tools) doesn’t support Unicode well. Perhaps that is the case, but I am had pressed to believe that if people thought it had any value they wouldn’t simply add support to their tooling for Unicode. Fonts seem to be the biggest practical issue; lack of a supporting font usually results in an ugly box in place of the character. In the end I suspect that the worst culprit here is simply that Unicode in the code is a taboo: people simply won’t give it a try until a thought leader or two sheds light on the power to facilitate communication that Unicode brings.
Until then, you will have to be happy with Emacs and DrScheme.

Software repository mining with Marmoset

Most computer science educators hold strong opinions about the “right” approach to teaching introductory level programming. Unfortunately, we have comparatively little hard evidence about the effectiveness of these various approaches because we generally lack the infrastructure to obtain sufficiently detailed data about novices’ programming habits.To gain insight into students’ programming habits, we developed Marmoset, a project snapshot and submission system. Like existing project submission systems, Marmoset allows students to submit versions of their projects to a central server, which automatically tests them and records the results. Unlike existing systems, Marmoset also collects finegrained code snapshots as students work on projects: each time a student saves her work, it is automatically committed to a CVS repository.We believe the data collected by Marmoset will be a rich source of insight about learning to program and software evolution in general. To validate the effectiveness of our tool, we performed an experiment which found a statistically significant correlation between warnings reported by a static analysis tool and failed unit tests.To make fine-grained code evolution data more useful, we present a data schema which allows a variety of useful queries to be more easily formulated and answered.

Here is the ACM portal page.
(via the PLT Discussion List)

Sugar – Release 8.2.0

Sugar is the UI portion of the Linux build that runs on the OLPC XO.
It is a radical departure from what we would call “typical” user interfaces in 2008; and it really took some “getting used to it”. With the release of 8.20, it looks like they have made some “user friendly” Sugar and a few other things, too:

It took guts to come up with Sugar, and perhaps even more to make these kinds of changes. As minimal as they seem, they are not insignificant.
Disclaimer: I have not yet tried out this build as my XO is currently out on loan.
(via OLPC News)