Martin Geisler Online

I haven’t updated GimpsterDotCom lately, sorry about that :-(

Let me just give you a quick recap of the last few weeks… I had my Easter Holidays, and it was great. I spend a couple of days visiting my family in Aalborg, and I spend the rest of the time here at [Skejbygård][], enjoying the sun and the wonderful people you find here.It really made me long for the summertime which is just around the corner…

When I got back to [Skejbygård][], I discovered that Kristian Kristensen was going to Århus for a MicroSoft seminar on DotNet. So we met afterwards his seminar and I gave him a tour of DAIMI at the University of Aarhus and Århus itself before I showed him [Skejbygård][] so that he finally could see how and where I lived. It was really great to get together and talk about “old days”.

We’ve also had a “Decade Party” here at [Skejbygård][]. The name “Decade Party” means that the music that was played was grouped into music from different decades along the evening. We started with dinner for all of [Skejbygård][] at 19:00 and then the party was held afterwards. At 21 to 22 the music was from the 1930s: swing with the bartenders were dressed up like people from an old gangster movie. Then there was music from the 1950s, 1970s where Martin Justesen made a great performance as John Travolta from Saturday Night Fever, 1980s, 1990s and then just comtemporary music. It was a really great idea and the party was a huge success!

Ahh, there’s just a single day left until the Easter holidays start, and I’m only having three hours tomorrow accourding to my schedule!

Not that I’ve been studying all that much the last couple of days… I sat down yesterday and tried to make the Turing Machine that would take an input tape with “aaaaaa#aaaaaaaaa” and turn it into “aaa“.

In other words: calculate the greatest common divisor of m and n represented by the input a^m#a^n. In the above case, the greatest common divisor of 6 and 9 is 3 if I’m not mistaken.

It turned out that Turing Machines are extremely annoying to program! Even the simplest operation gets enormously complicated. Somehow I managed to sit up all night trying to get things to work — I just kept tweeking and changing my program, hoping to catch that finaly special case that ruined the result. Amazingly I didn’t get that tired, it’s as if you reach a point and from then on you can carry on. But I still have a bad feeling that I’m going to get really tired soon…

I used a rather nice program called gturing to test my program, which you can find here. The comments are in Danish, sorry about that, but I used the program in a Danish hand-in exercise and when I rewrote things this morning I changed the English comments into Danish ones so that they would be easier to use in the report. I believe that the program now handles all correct input correctly. Correct input is input that matches the RegularExpression “a^m#a^n”.

The program also handles cases like “#“, “aaa#“, and “#aaa“. With the first input the machine calculates gcd(0, 0) = 0, the two other inputs represent gcd(3, 0) = gcd(0, 3) = 3. The reason why gcd(0, 0) = 0 is, that gcd(m, n) is defined as the unique whole number d that satisfies

Div(d) = Div(m) intersect Div(n)

where Div(n) = { d in N | d divides n }. Here we have that Div(0) = N, that is, all natural numbers divide 0 — take a natural number and multiply it with 0 to see for your self. So we look for a number d that satisfies that Div(d) = N. The only number that has this property is 0 itself, so this means that gcd(0, 0) = 0.

Mikkel Krøigård and I finished the assignment for DAIMI:dDist Thursday evening as we had predicted. After that I just relaxed, I don’t know what Mikkel did, but I suspect he did the same :-) It was really finally to get way from the project which we’ve coded quite a lot on all last week. We don’t even get a grade for it, we just have to have it approved before we’re allowed to attend the aural exam that will be held all too soon now.

After my last post you could the get the impression that I’m tired of running such an open WikiWikiWeb where everybody can change everything so easily. Nothing could be more wrong! When I explain the concept of a WikiWikiWeb to people most of them find it rather strange — they don’t understand how it could work.

But it does work. From time to time I see people correcting errors found on the pages here at GimpsterDotCom, making the site a little better each time. For example, after I restored [PHP Shell][], someone was kind enough to change the word “lunched” into the correct “launched” so that the page now make a lot more sense. I’m very grateful for those corrections because they’re the kind of mistakes that are hard to catch for me when I don’t speak English natively.

It’s these small and large contributions that proves to me that WikiWikiWeb~s work and I would like to thank everybody who have helped me since I launched (note, not lunched :-) GimpsterDotCom as a WikiWikiWeb.

Don’t people have anything else to do than mess up my pages?! Yesterday I made a new release of [PHP Shell][], and 13 minutes later some idiot (with an IP address of 12.151.162.13) replaced the entire page with the text “H A C K E D B Y A L N O R 3 S”.

First of all, you haven’t “hacked” anything — you’ve used the readily available editing facilities in PhpWiki to edit the page. Now, that’s really impressive — it shows that you can submit a form through a webbrowser! What a cool way to demonstrate the great computer skills possessed by the so-called hackers from this “alnor3s”… I guess we all have to fear these guys who have such great knowledge on how to do WikiVandalism…

Secondly, the term hacker is used about a person who enjoys exploring the details of programmable systems and how to stretch their capabilities, as opposed to most users, who prefer to learn only the minimum necessary. according to JargonFile:hacker. Perhaps you confused yourself with a cracker (see the Jargon File), but I wouldn’t even call you that since you haven’t cracked anything — a WikiWikiWeb is already wide open to everybody.

Even if you have no creative skill, there’s no reason to destroy the work or others, especially when this work is given away for free in the hope that someone out there might find it useful.