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Diary, September 1996

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Thursday, September 5, 1996

About security

Our rooms have one of the most advanced key systems `Electro LIPS', making use of keys which has a chip with a unique identification code. It is a very flexible system as each lock can be (re)programmed to work with any number of keys. In case a key gets lost, and might fall in the wrong hands, the locks can simply be reprogrammed.

Each lock has its own power source consisting a pack of batteries, and the lock starts beeping when they are getting empty, as a signal that the batteries have to be replaced. The battery compartment is only accessible when the door is open, so, if you ignore the beeping, the door might one day not open at all anymore. Only brute-force will then be left as a means to open the door.

Apparently, and you would not believe it in a building full with educated people, this has happened several times in the past years, as last week when the locks were serviced they turned the handle bars inside-out.

Although this might look like a trivial thing, anybody can break in the room within a few minutes, as now the little screw holding the two parts of the handle bars together is on the outside. removing this screw allows you to remove the handle bars, but what is more important also the front plate. And once you have opened the front plate you can remove the lock, after which the opening of the door is a triviality.

Book review

Below follows a quote from a book review by
John Mark of the book `Take and Read: Spiritual Reading - An Annotated List' by Eugene Peterson (Grand Rapids: Eerdmans, 1996) (author of The Message):


Today's (electronic) campain is on informing everybody that the University and it's campus will not have any water next Saturday between 7 and 9 AM. I already saw several emails and news postings about this.

Holiday effect

It is now about 10 days since we came back from our holiday trip to China, and I can conclude now that it has been benificial to be away for four weeks. This kind of holidays realy give you a fresh motivation to do many (new) things. It is like a long holiday works as an eraser, and takes away alot of negative feelings and habbits, some of which you might not be aware any more of having.

The last days we have had clear blue skies for most of the day, at reasonable temperatures.

Friday, September 6, 1996

One of the puzzles mentioned in the rec.puzzle archive is: A solution is given by David Karr. I wondered what would be the answer to: I think the answer is (n > m):
total = sum i(m - i)(n - i)

Chris Date about Relational Databases

(Taken from an seminar announcement.) This is all explained in the paper: The Third Manifesto by Hugh Darwen and C.J. Date (more).

The mystery of disapearing potato peeling knifes

Many years ago, when I was still living a dormitory, every year there would be some freshman thinking he was smart, and buy four of five potato peeling knifes, complaining that we only had one. But all of us knew that this was a waste, because after about a week, we would be stuck with one potato peeling knife again. Where all the other knifes had gone, nodoby would know, but we all figured out that it was most likely that they had been thrown away with the potato peels. You can guess why this did not happen with the one potato knife left: every body needed it (for other small jobs).

Tuesday, September 10, 1996

I woke up at 7 o' clock, which is rather early for me, but now my sense for time seems to be disturbed. Yesterday evening, I played a game of Go against the program IGO by David flotland, which can be downloaded for free. I have been thinking about a simple script to turn it into a PostScript file, with each board situation on a different page, which should be rather compact using the right techniques.


The entry page of Rain Crow Publishers showed an interesting logo.

Wednesday, September 11, 1996

The `rather informal' paper The Primary Pretenders, by J. H. Conway, R. K. Guy, W. A. Schneeberger and N. J. A. Sloan, explains why the following is an interesting number:

Go game record in PostScript

I finished the program (which I suggested yesterday) for converting a game record (like this) to a PostScript file (like this). To do this I used the following command:
go2ps <ff960909.txt >

Thursday, September 12, 1996

In Expressions that talk about themselves the following excersise is given: I posted this to rec.puzzles and comp.programming.contests with the remark: Have fun!

Cycles in mail circulation

Most mail servers have the ability to redistribute email (by sending it to a list of email addresses), or to automatically reply to an email (by sending it back to the originator). This makes it possible that email start to circulate between two or more email addresses. This is what happened just before I left. I am in a mailing list which sets the `Reply-To:' field to itself, which means that any reply is send to the mailing list. This is inherently wrong. About half an hour after I had received an announcement about the KELM'97 workshop, I (and with me everybody else on the mailing list) received another messages, which started of with:

   The message cannot be delivered because the
   recipient's mailbox contains the maximum number of
   messages, as set by the system administrator.  The
   recipient must delete some messages before any
   other messages can be delivered.
followed by the original message. I quickly informed our helpdesk, before I went home, wondering how many messages I would find in my mailbox tomorrow.


Friday, September 13, 1996

It stopped

Half an hour after I left the office yesterday, there was another message starting with the same `Mail box is full' notice, followed by the message that I had received half an hour earlier. (This message contained the `Mail box is full' notice twice.) Luckly, through some human intervention this was stopped, otherwise, I would have just got an message which would contain the `Mail box is full' notice 33 times!

I wonder whether they have changed the `Reply-to:' field now. We, here in our group, already have been thinking about just replying to this each message with something like: Can this stop.


Red-brown patches have occured in the trees outside.

It is raining violently on and off.

September, when the fall sets on, is a special month.

There was a RFD posted for a nl.eternal.september.

Sunday, September 15, 1996

Today, Paul van Norden, preached about Luke 15:11-32, the story about the prodigal son, which is really about the elder sun, and not the younger one, as he explained. I have known Paul and his wife Yolanda since 1981, shortly after I moved to Enschede. The past four years they have been working in Berat "the town of a thousand windows", Albania.

Zuster Bouwman

It was announced that Zuster Bouwman, a lady from our church who is in her mid-eigthies, has become seriously ill. She already suffers from cancer for a long time, but is seems her condition has become worse in the past days. People from our church have volunteered to stay with her during the night, and help her husband with the housekeeping during the day. She might be too weak to visit her. I immediately wrote a card to her, and send it today. I pray that God may confort her in these days, which might well be the last days of her life here on earth.

I have never known my grandparents very well. For the day I came to know them, I have somehow considered them as the kind of grandparents I would like to have. They are the youngest (in spirit) old people I know, always ready to learn more. Through them I learned that even if you are old, life is worth living, and can be a true joy.


Monday, September 16, 1996

Situation Puzzles in the News

( This is taken from a news posting to
rec.puzzles posted by David Spero )

Just as I thought: that gas cap thing was too easy, mainly because it's probably happened to everybody! But here's two much harder ones, taken from today's media.

A Man writes an insipid novel purporting to reveal nine cosmic truths held by an aboriginal people in South America. The writing is terrible, the plot is silly, and the revealed wisdom almost meaningless. Yet the book tops the best seller list for over two years, makes millions of dollars, and starts a cottage industry of self-help based on its principles. How could this be?

And on a much more frustrating and terrifying note:

A Central African tribal group's leaders start a movement based on killing every single member of other tribes living in their part of the continent. They massacre nearly a million people before fleeing across the border to refugee camps in a neighboring dictatorship. In these camps, they rearm, go on murderous forays into surrounding territory, and prepare to resume their genocidal war on the country they came from. Yet international relief agencies including the Red Cross and the UN High Commission on Refugees spend over $1 million per day, subsidizing these camps, providing food, health care and even jobs to the people there.

The relief agencies know what the camp leaders are doing, and have condemned it. Yet they say they cannot move against the thugs, and they cannot stop their massive aid program,even though everyone knows they are setting the stage for future genocide. Why?

Scientifical evidence that intercessory prayer works

Today, I found a reference to an article with the title Positive therapeutic effects of intercessory prayer in a coronary care unit population, which claims that intercessory prayer realy works.

Tuesday, September 17, 1996


The third Tuesday in September is called `Prinsjesdag' (Day of the little princes), because it is the day that our Queen (or King) rides to the parlement in a golden carriage to read out-loud the plans of the parlement.

Today, Rolf, my former boss, flew to South-Africa for another birding trip.

The goat puzzle

The puzzle:

The solution:


Alternative puzzle:


It was in the first week of August 1977 that I worked on solving this puzzle for the first time during the holidays together with a cousin. We did not manage to solve the puzzle.

Monday, September 23, 1996

Alte Bekannte - Neue Gesichter

Alte Bekannte - Neue Gesichter (old friends - new faces) is a photograph book by Helmut Hartwig. When I bought this book it was wrapped in white paper, on which there was a sticker with the following text:
     Alte Bekannte - Neue Gesichter,   Helmut Hartwig
     Fotografische Begegnungen mit der Bahn.
     Limitierte Vorzugsausgabe
     Handsigniert und numeriert
     ISBN 3-923937-79-2                DM 98,-
     Dieses Buch trägt die Nummer 1028
When you remove the paper you see that the book is in a box, on which it says Limitierte Vorzugsausgabe, which means that only a limited number were printed. My copy has the number 1028 written by the author on the inside. The book also contains an autograph of the author. On the cover of the book there two small photographs have been clued. As the sub-title says, the book contains photographs from old and new trains and railroads found in Germany. I paid 12.95 guilder for the book, which is almost one tenth of the original price (DM 98,-) mentioned on the paper.

Collecting books

It is a long time ago, since I bought a book like the above book, which I consider good enough to be added to my collection. For a book to be added to my collection, it must be a work of art in itself.

De Slegte

The name of the bookshop where I bought the book is called `De Slegte', It is a bookshow which sells books which are left over from regular bookshops (usually, because they could not be sold anymore), and (of course) second hand books. For this reason, the prices are usually very low. I visit this bookshop almost every Saturday. It has three floors, and a small balcony between the first and second floor. The second floor is completely dedicated to second hand books. Half of the third floor is used for books related to computers.

De Slegte has several bookshops throughout the country. I like their bookshop in Utrecht, which is build inside an old house along one of the cannals. When you think you have found the top-floor you discover a small winding stair, which leads to some additional floors.

One very typical thing of de Slegte bookshops is that the always wrap your buyings in brown paper.

Calpournius Piso

Ever heard of Calpournius Piso? Me not, but read the following news posting: After some searching I found some a page about the alleged piso family. Seems some people like to make fun. I also found out that the booklet is more than 10 years old.

Ten digits count themselves

Mariza Cabral posted a puzzle about ten digits that count themself such that the i-th digit is equal to the number of (i-1) digits in the number.
Pat Vennebush thought that this was better stated as follows: Make the following statement true: `In this sentence, there are __ 0's, __ 1's, __ 2's, __ 3's, __ 4's, __ 5's, __ 6's, __ 7's, __ 8's and __ 9's.'
Then Mariza Cabral replied with: `You're right, that problem is formulated more nicely, however it is a different problem from the original one. This is because you must now count the digits that follow the blanks, not just the digits in the sequence that is to go in the blanks.' He also included: `In this sentence, there are _1_ 0's, _7_ 1's, _3_ 2's, _2_ 3's, _1_ 4's, _1_ 5's, _1_ 6's, _2_ 7's, _1_ 8's, and _1_ 9's.'
Ed Murphy told that th problem stated by Mariza is mentioned in Martin Gardner's book Mathematical Circus, chapter 11, problem 7, according to which the answer is: 6210001000. For base 4 the answers are: 1210, 2020. For base 5: 21200. And for base 6 and up: R21(0...0)1000, where R equals base-4, and such that there are (base-7) zeroes in the parentheses. (This is specified as unique for bases 6 through 10, but for higher bases it merely says that this is *a* solution. The reference Gardner cites may prove it unique, but he doesn't say so.)
Guyon Roche then wrote: How about... ``In this sentence, there are _1_ 0's, _11_ 1's, _2_ 2's, _1_ 3's, _1_ 4's, _1_ 5's, _1_ 6's, _1_ 7's, _1_ 8's, and _1_ 9's.'' How many solutions are there?
The answer to the last question is: there is no other answer than the one mentioned here on this page. I verified this with a small


Tuesday, September 24, 1996

Piet Mondriaan

I bought a catalogue of an art exhibition of
the works of Piet Mondriaan at De Slegte bookshop. He is a Dutch painter that is especial famous for his painting consiting of a grid of black lines, where some of the rectangles are coloured with red, blue and yellow. The book has pictures of most of his paintings, and a short biography of the most important events in his life, sorted by date.

Thursday, September 26, 1996

At the moment it is a few minutes after three o' clock in the afternoon (local time, of course). I am in the middle of some heavy coding, which calls for a short break. What follows is a list of things that caught my attention in the past day:

Friday, September 27, 1996

Julia set of the caulifower fractal

This morning, while playing with Annabel, so that Li-Xia could dress her, I still found myself thinking about the fact that the Julia set of the cauliflower fractal can be described by infinite sets of equations. In a sense it is not so strange that I was thinking about it, because it has been on my mind, since yesterday evening when I listened to a talk about chaos and fractals. But what was strange, is that I was thinking about something of which I am sure Annabel does not have the faintest idea that it might exist. Of course, her perception of the world is so different than mine, but I am not sure that she will ever understand these thoughts when she has grown-up.

Ten digits that count themselves

Fred Galvin wrote: `This puzzle goes by the name logic/self.ref in the rec.puzzles archive. For more information (bibliography, generalizations, and a simpler proof than the one in the archive) see the letters to the editor (by Steven Kahan, Lee Sallows, and somebody by the name of Fred "Gavin") on pp. 276-277 of Mathematics Magazine, vol. 66, no. 4, October 1993.

Mid-autumn festival is coming

May I wish you:

            Dm           mmDm  Dm       Dm    Dm         m   mmmDm
       m    DD    m    ""Dm    DD  m    DD  mmDDmmDm     DD""D"
       DD"""DD"""DD"  mmmDDmDm DD mD"  mDDDm  DD DD      DD  DD
       DD   DD   DD     mDDm DDDD""   D"DD "  DD DD    mmDDmmDDmmDm
       DDmmmDDmmmDD    mDDD"D" DDm      DD """DD"""""     m  DD m "
       DD   "    m" DD   D" Dm     DD   DD"Dm       DD" DD  Dm
            DD           DD mD"  "Dm    DD  DD   DDm   mD" m DD   "Dm
            D"           D"m"     "D"   D"m""     "D" "     "D"    "
(I received this from Zhu Zhiting, East China Normal University)

Tail tail division

void main(int c,char*v[]){int d,a;if(c<3)return;a=atoi

The Universe

I had a look at a picture taken by the Hubble telescope.

Talking to Annabel on the phone

I just talked with Annabel on the phone. This was the first time that she was talking back, not that it made much sense, but she really replied to what I said.

Sunday, September 29, 1996

Zuster Bouwman

Today, we heared that zuster Bouwman passed away yesterday. She is save with the Lord Jesus now, as she firmly believed. In the past two weeks she has suffered greatly, but she witnessed that there was always a joy in her heart that no one could take away from her. She now has ran her race, and come to the finish of her life.

But still it is a great lost, in the first place for her husband, broeder Bouwman, for whom it must be difficult to continue on his own in his high age. We pray for him. But also for our church this is a great lost. I will miss her. A date for the funeral has not been set. I very much would like to attend the funeral.

(About the date of her funeral. Follow-up)

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