Large parts are written in x86 assembler, but I’m still a big fan.

www.stripedgazelle.org/joey/dreamos.html

http://www.dreamsongs.com/Files/DesignBeyondHumanAbilitiesSimp.pdf

Gerald Jay Sussman, We really don’t know how to compute
http://www.infoq.com/presentations/We-Really-Dont-Know-How-To-Compute

I do really enjoy Sussman’s talks, even more than the SICP book.

Key points: Software Development’s big problem is Evolvability, not Correctness. Alternative ways to think about program design (architecture, if you like) may open doors. Different examples are shown:

• Symbolic differentiation using generic functions and a crazy mathematical trick.
• Using propagator networks to resolve constraint systems with multiple numeric variables.
  Then using generics to use the same propagator network with interval values.
  Then propagating provenance of values along with the values.

Some math and basic Scheme programming is required for this talk. It makes you want to build a propagator network. In case you understood the first example, it probably makes you want to implement that as well.

(A quick Google search showed that it might actually be described in the book “Structure and Interpretation of Classical Mechanics, of which Sussman is a co-author.)

Rich Hickey, Simple made easy
http://www.infoq.com/presentations/Simple-Made-Easy

On the difference between simple and easy, what programming techniques Rich Hickey considers good based on that reasonsing. Interesting perspective on how to build abstractions and on components that have coupling even though they only speak to each other over interfaces.

Take aways: “Easy” doesn’t mean “simple”, and “simple” doesn’t mean “easy”.

Opinions I agree with: There’s a balance between being able to prove a program and it being generic and flexible (e.g. usable in the real world).

Opinions I am critical of:

• Rich Hickey pokes fun at people who do testing and refactoring by comparing failing tests with running your car into a traffic barrier to stay on track. The argument is invalid, because in software testing, the car is of course only run into the traffic barrier within a controlled and isolated program setup. The other reason why it’s incorrect — but that is my own anecdotal evidence only — is that without tests, I tend to run off track at some point, and it’s just nicer to notice it. Software development is just harder to do than driving a car.
• Objects are only meant to encapsulate driver software and we should manipulate all basic data structures (maps, sets) directly instead of encapsulating them. I disagree with this, but it’s really hard to argue these things.

In case anyone decides to watch both talks, I suggest first watching the talk by Gerald Sussman, because it actually happened earlier, and Rich Hickey makes some references to it.

http://james-iry.blogspot.com/2009/05/brief-incomplete-and-mostly-wrong.html

http://nyan-mode.buildsomethingamazing.com/

http://ridiculousfish.com/blog/archives/2010/07/23/will-it-optimize/index.html

If you’re programming C or C++, you should have a look. It’s a fun (and interactive) page and a good read.

Lesenswert, auch wenn man die vorkommenden Blogger und Kommentatoren in Fachschaftskreisen nicht mehr bekannt sein dürften. Und das beste ist: Eine Kopie von Dijkstras handschriftlichem Traktat (so es denn das selbe ist) hängt mitsamt neongelber Markierung dieser markanten Textstelle noch immer im Flur zwischen den AGs von Herren M. und P.

Ich habe mir den allergrößten Teil dieses Beitrages verkniffen. Einerseits muss ich nicht meine vollständige Meinung zum Thema öffentlich kundgeben, andererseits fürchte ich meine Leser zu langweilen. Ich diskutiere alles aber gerne per E-Mail. :->

Duff’s device — There was a time when putting a do loop around a switch statement’s cases would allow you to unroll the loop. I’ll spare you the uglyness here, have a look at the wikipedia page for the source code.

Fast Inverse Square root — This is incredible: You can approximate the inverse square root of a 32-bit floating point number by pretending it’s an int and doing some fast integer operations involving a fixed magic constant. (I came across this via this post about a similar method for calculating double reciprocals.)

I guess the second of these hacks is harder for the compiler to do on its own…

Stop reading weblogs at work!

I am happy to announce that Daniel Berger is now running the service for the students of the TU Kaiserslautern’s CS department. Along with the move, he also updates the software and tweaked the HTML template a lot. It isn’t obvious at first sight, but the page is alreay way niftier in many details (colored source code for example. Yay! )

Thanks for doing this! I had a great time building the website, and I hope you will, too.

This is not an average programming course: Topics covered are a range of different programming models like functional programming, logic programming, data-directed programming (OO is a specialization of that) as well as stream-oriented programming.

I read this book pretty late in my studies, and it still lead to an amazingly large number of “Aha” moments.  One of my favourite ones is the example which motivates procedural abstraction (first-class functions).  It also contains insightful discussions of layered system design and a number of interpreters are built for different Scheme dialects, including one with lazy evaluation and one with ambiguous values.  Finally, its last chapter discusses how to implement (dynamically typed, garbage collected) languages on register machines (real processors).

It is an ever-ongoing discussion whether this book it suited for beginners.  Amazon’s review page contains some very strong opinions in both directions.  While I can’t judge this, I can definitely recommend having a look at the lecture content in text or video form, because it’s available free of charge:

• http://mitpress.mit.edu/sicp/ — Book website, including full text in HTML format
• http://groups.csail.mit.edu/mac/classes/6.001/abelson-sussman-lectures/ — Video lectures (highly recommended and often very entertaining!)
• Wikipedia has a more complete and up-to-date list of links on SICP.

Back in about 2005, a friend told me he wanted to write a program which uses the Scroll Lock LED to display morse code. Here’s what we ended up with back then.

bsdgames and X11 required.

#!/bin/sh
exec morse -s | sed -e 's/\./xset led on; sleep 0PUNKT1; xset led off; sleep 0PUNKT5;/g' -e 's/\-/xset led on; sleep 0PUNKT3; xset led off; sleep 0PUNKT3;/g' -e 's/PUNKT/\./g' -e 's/MINUS/\-/g' -e 'a sleep 0.6' | sh

Who needs an interpreter when you can do code transformation with sed?

M-x list-colors-display gives an overview over Emacs’ supported colors.

Mapping the Caps Lock key to Ctrl really paid off for me. It sounds unbelievable, but I noticed that I need way fewer looks at the keyboard when typing now. You suddenly really get to keep your hands in the same place when typing.

I really can’t miss this anymore, I find myself hitting Caps Lock on other people’s computers again and again. :->

If you’re like me, and you use Caps Lock only for the occasional environment variable, just give it a try. The transition was really easy for me (Hint: In the first few days, it was helpful to remove the left Ctrl key, to avoid falling back to old habits.).

Here’s how this is done:

Mac OS X

System Preferences –> Keyboard and Mouse –> “Keyboard” tab –> Modifier Keys… –> Select Control for the Caps Lock key.

Mapping Caps Lock to Ctrl (Mac OS X)

GNOME
It can be found somewhere in the keyboard settings dialog.

Plain X11 (for users)
Can be done using a .Xmodmap hack.

Plain X11 (for admins)
Do your users a favor by making Ctrl on Caps Lock the default: To /etc/X11/xorg.conf, add
Option "XkbOptions" "ctrl:nocaps"

to the section “InputDevice”. (On Debian, you can also run dpkg-reconfigure xserver-xorg, which makes it a bit easier.)

Linux console (Debian)
In /etc/default/console-setup, add XKBOPTIONS="ctrl:nocaps".

Riccardo Mottola posted a Screenshot on his weblog. You rock!

The Grr RSS Reader is developed by the GNUstep Application project. (No binaries for download there currently — this is just a development version.)

In .emacs:

;; Color theme.
(require 'color-theme)
(if window-system
    (color-theme-deep-blue)
    (color-theme-arjen))

In .Xresources:

Emacs.font: Monospace-11

Fonts can also be set from within Emacs itself, but putting it in .Xresources allows you to break your .emacs without losing the font size. Do a xrdb -merge .Xresources to use this in a running X window session.

Currently, David continues hacking on the implementation (while I am busy with university, which is of course more important). Parsing the OMeta grammar works for him as far as I know, he probably gets it running soon. When it works, this will be a very nice foundation for Etoile’s programming language parsers. Especially, parsing Smalltalk expressions for the workspace will be pretty simple then. And who knows what we will be able to use it for apart from that. Alessandro Warth’s thesis has some pretty impressive examples for what it can be used for.

You want to play around with it? OMeta/JS — the JavaScript variant — is really great for that. First, it works in your web browser, so you don’t have to install anything. Second, it’s built like a Wiki, so it automatically comes with lots of example source code from other people playing with it.