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I write, therefore I am

With this variation on a famous statement by the philosopher Descartes, I would like to express that the act of writing about what happens in my life is important to me.

Thursday, December 1, 2022

Advent of Code

I have decided to use literature programming for this years Advent of Code and not to compete with others. See this GitHub repository for my progress. I already made some improvements to MarkDownC. I also started developing a language for Advent of Code puzzles. I have no idea how that is going to work out.


Wednesday, November 30, 2022


Tuesday, November 29, 2022


At 16:57:20, I bought the book Geschiedenis van de moderne literatuur written by Herman Brusselmans in Dutch and published by Prometheus in 2021, ISBN:9789044648904, from bookshop Broekhuis for € 17.95.

Saturday, November 26, 2022

Going into the city

I went biking to the city center. I walked to Fotogalerie Objektief where I saw the exhibition Bomen in het park (Trees in the park) by Ruth Lowie. I went to Concordia, where they did not have any new exhibition. I looked at the books at the low round table in the middle of the exhibition Doublet: Thijs Ebbe Fokkens & Silke Schönfeld and I made notes of the titles of two of them: The Immortality Key: Uncovering the Secret History of the Religion with No Name by Brian C. Muraresku and being aware of being aware by Rupert Spira. I also visited bookshop Broekhuis, where I spend almost an hour looking at the new arrives. When I noticed that the sun was about to set, I decided to go home, to enjoy the last light of the day while going home. On my way home, I took the following picture on the 'square' called Usselerplein, there where the Usselerweg ends at the Denneweg and continue into the Zweringweg (position in street view).


Friday, November 25, 2022


Thursday, November 24, 2022


Wednesday, November 23, 2022


Tuesday, November 22, 2022

Palindrome date (DD-MM-YY and YY.MM.DD)

Today is a palindrome date when written according to the DD-MM-YY format: 22-11-22 and the YY.MM.DD formats: 22.11.22. The previous such date was November 12, 2021 and the next will be November 3, 2030.


Monday, November 21, 2022

Patches of snow

This morning, when I biked to my office, I saw some patches of snow. I saw some layers of snow on some car roofs and from this I conclude that about 0.5 to 1cm of snow fell during the night. Only at the end of the night (after 5 o'clock) the temperature dropped below zero, reaching a temperature of -1.4° Celsius at Twenthe Airport. The night before the temperature dropped to -8.2° Celsius, which is not a record, but this rather exceptional. In the middle of the province Overijssel one weather station reported 4cm of snow.

Sunday, November 20, 2022


In the past weeks, I have been working on trying to prove that it is indeed possible to create infinite irregular grids of squares and equilateral triangles. I wrote a program for manipulating vertex labeled graphs. The program constructs two vertex labeled graphs, calculates the product of these graphs, prunes any dead-ends, and checks that all edges in the original graphs is still represented in the product graph. If that is the case, it means that there is a matching between the two graphs (on the labels) such that for any infinite walk in one them, there is also a path in the other graph. Because the two labeled graphs are related to the edges of all possible sequences of triangles and squares, it proves that above and under any sequence.

Thursday, November 17, 2022


Wednesday, November 16, 2022


At 16:06:24, I bought the book Limes atlas edited by Bernard Colenbrander, written in Dutch and published by 010 Publishers in 2005, ISBN:9789064505355, second-hand from Polynea (webshop) for € 75.00. (The book will be send to me through a package delivery service.)


Saturday, November 12, 2022

15.3° Celsius

The temperature at Twenthe Airport has gone up to 15.3° Celsius, which breaks the previous record of 14.9° on this date in 2015. This is the tenth warmest day record of this year. Below a picture that I took this morning of a Garden marigold (Calendula officinalis) flower, which I sowed on Sunday, April 10, 2022. The normal flowering periode is from may to november.

Thursday, November 10, 2022

De Meer 1

Conny and I visted Castellum Hoge Woerd were we saw the exhibition about De Meern 1, a 25 meter long Roman ship that sank due to an accident based on the fact that many tools and personal items were found in the area the cabin was located. A unique find and quite interesting. We also saw the exhibition Natuur in Eenvoud with sumi e painting by Martha Goedings and raku creamics by Anke van der Kwaak. We also visited the museum with many archaeological finds, but we did not find any information about the roman castellum, if it was indeed located at the location of the Castellum Hoge Woerd, which has the form and size of the castellums found in the Netherlands.

Wednesday, November 9, 2022


This morning, Conny and I, walked through some of the many alleys in Utrecht. We walked through the following (where the numbers in square brackets refer to the numbering used in Stegenboek, rapport en kaart): Around noon we arrived at the Domplein (Dom Square), which is where the nave of the St. Martin's Cathedral (usually refered to a the Domkerk) used to be, which on 1 August 1674 was destroyed by a summer storm, maybe including a bow echo (see: A reconstruction of 1 August 1674 thunderstorms over the Low Countries). The nave of the church was never rebuild. We did the DOMunder tour. After some introduction, we descended under the Domplein to view the excavations. These excavations proved the presence of the Traiectum and established it location to included the current square. It was interesting to hear the 2000 long history of the square.

At the end of the afternoon, the evening we visited bookshop Broese at the new location that they moved to. I was a bit disappointed. The shop felt very crowded and the amount of ramsj (sale of new, hard-to-sell books at reduced prices) has been reduced greatly and placed in a 'corner' of the shop. The exact science section of the bookshop had no books on math and physics, but did have a lot of management related books.

We had dinner at Silk Road, where we had dishes from Route 1: naan, zeitun, hummus, muhammara, murgh massale, kofte, tabouleh, bahar, and Route 2: naan lahasun, baba ganoush, hummus mazara, dahl, tajine, dopiazza gosala, salat mazara, kaeng kari kai, plov. We also had some desert. Although the dishes did not look large, it was still enough and definitely a very nice experience with a lot of interesting tasts.

We also walked through some alleys, the first two on the way to the restaurant. These are:

We also saw the light art work of Utrecht Lumen at Buurkerkhof.

Tuesday, November 8, 2022

Dutch water line

This afternoon, Conny and I visited the Waterliniemuseum, which a museum is about the Dutch water lines, which by means of indundation were used by defend against attacks by foreign countries. The museum is inside the fort near Vechten. This fort is one of about fifthy that are part of the New Dutch Water Line, which was meant to defend the provinces North Holland, South-Holland, and the west part of Utrecht including the city Utrecht. The old water line did not include Utrecht.

Next, we visited Castellum Fectio, which is just west of the fort. It is part of the Limus Germanicus, the northern border of the Roman Empire and the unsubdued Germanic tribes. The next castellum (fort) to the west, is Traiectum, which is located in the center of Utrecht. The book Limes atlas has some interesting maps explaining the position of limes and the various Roman forts in the Netherlands.

We went to Utrecht were we are going to stay for two nights. On the way to a Greek restaurant, we visited the bookshop Steven Sterk. At 17:55, I bought the book Actie-Reactie: 100 jaar kinetische kunst written by Serge Lemoine, Marianne Le Pommeré, and Emily Ansenk, edited by Charlotte van Lingen, written in Dutch and published by Lannoo in 2018, ISBN:9789401456234, for € 12.50.

After having our dinner at the Greek restaurant in one of the wharfs at Oudegracht, we walked through the city center, looking at some of the light art works that are part of Utrecht Lumen. We visited:

Monday, November 7, 2022


At 15:24:57, I bought the book Atlas van de wereldgeschiedenis: de geschiedenis van de mensheid in 515 kaarten written by Christian Grataloup, translated by Henriette Gorthuis from French into Dutch, published by Nieuw Amsterdam in 2020, ISBN:9789046827321, from bookshop Broekhuis for € 19.95.

Thursday, November 3, 2022


Wednesday, November 2, 2022

Rijksmuseum Twenthe

This afternoon, Conny and I visited Rijksmuseum Twenthe. We saw several exhibitions. We first went to see the exhibition Marinetti and Futurism: a manifesto for a new world, which is about Filippo Tommaso Marinetti and Futurism in Italy. Italian Futurism has some dark sides due to its support for Fascism. I found the following works noteworthy:

Next we saw the exhibition Homo symbioticus with works from the collection selected by the Dutch author Atte Jongstra. The details about the works on display were printed on some sheets held together with a staple, but did not cover all the works on display. Incomplete list of the works I found noteworthy:

Next we saw the Carlijn Kingma: The Waterworks of Money. I found the following works noteworthy:

We walked through the rest of the museum.

When walking back to the entrance through the corridor, we saw the exhibition The Setting of Violence: A photographic approach to Pier Paolo Pasolini's Saló o le 120 giornate di Sodoma (1975) by photographer and visual artist Rein Jelle Terpstra, which has editted frames from the film that show the many prominent futuristic paintings on the walls.

At 14:33, I bought the book 100 Artists' Manifestos: From the Futurists to the Stuckists edited by Alex Danchev, written in English and published by Penguin Adult in 2011, ISBN:9780141191799, from the museum shop for € 19.95.

Tuesday, November 1, 2022

61 years

I was born on Wednesday, November 1, 1961 at 9:45 in the morning (CET). That means that today, I will be 61 years according to the calendar and 22280 days old. But how old am I really? The tropical year, the time that it takes for the seasons to return, is said to be 365 days, 5 hours, 48 minutes, and 45.19 seconds. Today, around 4:19 in the night, it was 61 tropical years since I was born. But the tropical year is shorter than the sidereal year, the time taken by the Earth to orbit the Sun once with respect to the fixed stars, namely 365 days, 6 hours, 9 minutes, and 9.76 seconds. That means that, tomorrow at 1:03:55 it will be 61 sidereal years after I was born. The average anomalistic year, the time taken for the Earth to complete one revolution with respect to its apsides, is 365 days, 6 hours, 13 minutes, and 52.6 seconds. That means that, tomorrow around 5:51:28 it will be 61 average anomalistic years since I was born.

Saturday, October 29, 2022

22.1° Celsius

The temperature at Twenthe Airport has gone up to 22.1° Celsius, which breaks the previous record of 21.3° on this date in 2005. At the end of the afternoon, Conny and I made a walked just in our shirts.

The Overkill Festival

This evening, I went to The Overkill Festival. I looked around the exhibition. I liked the following art work, installations: When I was there, I also heard Chebedajha (SoundCloud) and Zeno van den Broek play on modular synthesizers.

Friday, October 28, 2022

22.7° Celsius

The temperature at Twenthe Airport has gone up to 22.7° Celsius, which breaks the previous record of 21.3° on this date in 2005.


Thursday, October 27, 20220


Wednesday, October 26, 20220


Tuesday, October 25, 2022

Partial solar eclipse

At 12:32, Conny and I watched the partial solar eclipse.

Monday, October 24, 2022

Our whole house has Alzheimer's

I went to Amsterdam to attend the PhD defense of Silke Hoppe where she defended her thesis Our whole house has Alzheimer's. How early-onset dementia shapes relationships of families in the Netherlands. It was held in Agnietenkapel (Announcement in Dutch). I took a copy of the defense at the entrance. The recording of the defense including an introduction. The introduction brought back some of my own experience when we were a family with Alzheimer's. It made me also realize how I have dealt with and overcome those experiences and also how they shaped my personal development. I think that practicing some forms of active meditation and practice mantra singing (around 2016 to 2018) has been a part of this.

Sunday, October 23, 2022


I was wrong about what I wrote that gi-st-004 was not found by the program for finding regular irregular grids of squares and equilateral triangles, because it was. But I did find that gi-dt-005 was not generated the program. I spend some time finding the reason for this. It had to do with the method I used to limit the search space for patterns. I had put a limit on the lines between the rows of possible pieces such that each can only occur once in each of the directions. When I changed this to a restriction on the rows of the possible pieces in the program, the missing pattern was generated. (It has been added to the dedicated page.) I am not sure if now all possible patterns are generated.


Friday, October 21, 2022

Do Androids Dream of Electric Sheep?

I finished reading the book Do Androids Dream of Electric Sheep? by Philip K. Dick, which I started reading on October 12 after I bought it on September 14. I found this book quite interesting and enjoyed reading it. The book is deeper than the film Blade Runner, which based on this book.

Sunday, October 16, 2022

Grid Index

This weekend, I had a look at the book Grid Index, which I received on Saturday, April 2, 2022 and which started me thinking about irregular grids of squares and equilateral triangles. I wanted to see if I could match the grids shown in the book, with the grids by the program irst.cpp that I wrote before and wrote about for the last time on Thursday, August 18. I quickly found an example of a grid, gi-st-004, that is not generated by the program. I decided to create a separate page about matching the grids with the results of the program.

Saturday, October 15, 2022

Going into the city

At Fotogalerie Objektief, I saw the exhibition On the Road by Bert Teunissen. I went to bookshop Broekhuis where I was met with a lot of parents with their children, some of which appeared not have been in the bookshop for a long time. This was due to the childrens book week, where you get a free book when you spend € 12.50 on children books. At 15:37:01, I bought the book Dagboek 1972 written by Jan Wolkers in Dutch and published by De Bezige Bij in 2007, ISBN:9789023425342, from for € 9.95.


Friday, October 14, 2022


Wednesday, October 12, 2022


December 2022
November 2022
October 2022
September 2022
August 2022
July 2022
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My life as a hacker
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The Art of Programming
eXtreme Programming


Hamilton cycles
cutting sticks
Califlower fractal




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