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Diary, September 2020

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Tuesday, September 8, 2020

Vitamin D

There is more and more evidence that vitamin D has a positive effect on how someone responds to a COVID-19 infection. A recent double-blind experiment showed that vitamin D is even a good treatment option for people who have been administered to a hospital: Effect of Calcifediol Treatment and best Available Therapy versus best Available Therapy on Intensive Care Unit Admission and Mortality Among Patients Hospitalized for COVID-19: A Pilot Randomized Clinical study. In the past weeks the number of registered infections has been increasing in the Netherlands, but so far this has not led to a strong increase of people administered to a hospital and the number of casualties. Only about 3% of the people who are being tested, test positive on COVID-19. Among the people who test negative, there also some people who have no symptoms, but have themselves tested because they came from a high-risk area or have come into close contact with someone who was infected. I have heard of several people who were ill, even with a few days of high fever. There seems to be some kind of other virus going round. You would expect that there are less infection now that people practice social distancing (albeit to a lower degree than at the start of the outbreak). One reason why there are not many people in hospital, is because it seems that mostly younger people test positive. Maybe that older people excersize more social distancing. Another reason could be that many people have higher vitamin D levels so shortly after the summer. So far, I have not heard any statements in the media about administering vitamin D supplements for people who are at risk to develop severe complications due to COVID-19.

Thursday, September 10, 2020

Dune 2020 trailer

Yesterday evening, shortly after six, I watched the trailer for the Dune (2020) film. When I saw it I was not sure whether this would be a good film adaptation. Even one of the first words in the trailer doesn't match the book, because Chani calls Paul Usul in his dream. And I also can't remember that the book speaks of a crusade (Paul in the trailer says: "There is a crusade coming"), but of a jihad, a holy war. This morning, I watched the Dune featurette. Now that I've seen this, I think it might be a good movie. I doubt whether all layers in the book will be addressed. Maybe some will only be recognized by those who have read the book. It is only after I reread the book last year, that I understood that it is (also) about a profound tragedy of someone who without realizing himself degenerates into someone he never wanted to become. Let's hope the film will be a great success, because it only covers the first half (more two thirds) of the book, and it would be nice if the second half and the following books are also made into films with the same cast.

Friday, September 11, 2020


At noon, I went to the GOGBOT exhibition, which this year is only held at a few locations. Due to COVID, the exhibition inside requires you to buy a ticket for a certain time slot. When I entered the exhibition some installations were not running yet. I found the following installations interesting:

Around 14:00, I went to TETEM art space to see the exhibition Reflecties (Dutch for reflections). If I am not mistaken, this is the first time that they open again for an exhibition. There were a lot of students entering before me and I had to wait some time to see the exhibition. At the start of the exhibition, I was offered a tablet, but I refused it, only to discover that it was required for each part of the exhibition. I was a little dissapointed as it felt a little like a physical website, more about a philosophical discussion than about art.

Saturday, September 12, 2020

Border poles near Coevorden

Conny recently bought the book Op zoek naar grenspalen (which translates as Searching for border poles) by Herman Posthumus, which give walking routes along border poles along the border with German and the provinces of Drenth and Groningen. Today, we decided to give the first route a try. We parked the car near the pumping station called De Mars south of Coevorden and close to the border between the provinces of Overijssel and Drenth and started walking along the canal. We first walked on the north side of the canal before I consulted the book and realized we should be walking on the south side of the canal. We had a hard time finding many of the poles that were mentioned in the book because there was a lot over overgrown. The poles we found are:
Next we drove a little further along the border and parked the car on the Europark Allee. The border makes bluges in both directions, following a ditch, in a kind of S-shape. There was a farmer who had land on both sides of the border along the ditch. Now there is some dispute about on which side of the ditch the border lies. Because governments on both sides of the border, wanted to create an in industrial area, now called Europark, he was expropriated. (The ditch is no longer visible and the main offices of Intergas have been build in the area.) He claims that he still owns the area of the ditch, because it was not bought by government parties on both sides of the border. And because there is also a dispute about the exact location on the border, he now has declared it an independ country called: "Vrijstaat Beukeveld". More information, in Dutch, can be found on the site

The poles we found there are:

Some links (in Dutch) with information about poles along the route that we took:

After this, we also walked around the city center of Coevorden, which used to be a fortified town.

Tuesday, September 15, 2020

32.1° Celcius

The temperature at Twenthe Airport went up to 32.1° Celsius, which breaks the previous record of 29.3° for the temperature on this date in 2016.

Sunday, September 20, 2020

PARR specification

In the past weeks, I have been thinking about the steps with which a formal specification of the PARR patterns could be transformed into the PARR generator, which I wrote last month. In a way it is also similar to proving the correctness of the program. I have come up with some kind of specification of the collection of all PARR patterns using a made up specification languages where types are defined as sets. There are three types of 'complex' values: list (denoted with square brackets), sets (denoted with curly brackets) and maps (denoted with curly brackets and a colon separating key and value). Sets stands for all enumeratable sets and Nat stands for a natural numbers (including zero).

Graphs = { { "V" : V, "E" : E }
         | V in Sets and 
           E subset { { v1, v2 }
                    | v1 in V and v2 in V and v1 != v2 } }

subgraph(G1 in Graphs, G2 in Graphs)
  = G1."V" subset G2."V" and G1."E" subset G2."E"

FullPARRgraph = { "V" : V, "E" : E }
    where { "V" : V, "E" : E } in Graphs
      and V = { [x, y] 
              | x in Nat and y in Nat and
                0 <= x and x < 4 and 0 <= y and y < 5 }
      and E = { { [x1,y1], [x2,y2] } 
              | x1+1 = x2 and y1 = y2 or 
                x1 = x2 and y1+1 = y2 or
                x1+1 = x2 and y1+1 = y2 or
                x1 = x2+1 and y1+1 = y2 }

PARR(nrp in Nat, nrl in Nat) 
  = { graph
    | subgraph(graph, FullPARRgraph) and
      size(graph."V") = nrp and size(graph."E") = nrl }

This is not really an executable specification, yet it contains everything to calculate the PARR function.

Tuesday, September 22, 2020

Second wave

It looks like the second wave of COVID-19 infections has arrived in the Netherlands (as well). The number of infection has steady risen in the past weeks. It is only last week that also the number of hospitalizations has gone up. In the past week they have doubled. It is likely that this will continue in the coming weeks. Last Friday some addition regional measures have been announced. This evening, I watched last Sundays episode of Zondag met Lubach. It explained how the problems with the number of test being available in the Netherlands is related to the choice of the government to have the tests being done by the fifty regional labs, which are tied to hospitals, and not using commercial testing capacity until recently. Hugo de Jonge, the current minister of Health, Welfare and Sport has stated that this was also to sustain the regional labs until after the COVID-19 crisis. The program also mentioned that one of the member of the Outbreak Management Team is the chairman of the Dutch Association for Medical Microbiology, which represents the microbiologist working at the regional labs.

Saturday, September 26, 2020

Border poles near Coevorden (part 2)

Conny and I continued our search for border poles near Coevorden. We looked at three different locations. Some poles where hard to find due to a lot of over grown. The poles we found are:

Sunday, September 27, 2020


At 9:58, I picked up a chestnut from the Helmerstraat (road) during our walk of this morning.

Tuesday, September 29, 2020


At 17:34:46, I bought the book Elsbeth Cochius: Begegnungen / Ontmoetingen written by Elsbeth Cochius and Gert Gerrits in German and Dutch, published by Stichting Programmaraad Beeldende Kunst in 2008, ISBN:9783981069327, from charity shop Het Goed for € 3.50.

Wednesday, September 30, 2020

A simple Git workflow

Git is a distributed version-control system for tracking changes in source code during software development. It is probably the most popular system at the moment. But it is also a very complex system, which can be used in many different ways. I also have noted that there is often some confusion about the internals of Git among people starting to work with it. Many introduction to Git, like Learn Git Branching, fail to explain the different workflows of working with it. Below, I present a simple workflow, which works good for a small team.

Although Git is a distributed version-control system, it is often used in a centralized manner, where there is a central repository and where everyone syncronizes work through this central repository. There are free Git repository services, such as GitHub and GitLab, which also provide additional features, such as issue tracking. It is also possible to set up a central repository on a file server using the "git init --bare targetdir" command. The common way of creating a local copy of a central repository is to use the "git clone path", where the path is either a link to a repository on a service or a file path to a respository on a shared file server. Before you start working, you should issue the following commands:

After a local clone of the central repository has been made, you just can start working. By default you are now in the master branch. If you have been working on some issue for some time or you have heard about someone else having pushed a commit to the central repository, you issue the command:

If there are indeed new commits on the central repository, this will stash your changes, pull these commits, and apply the set of stashed differences to the up-to-date state of your local repository. This could lead to merge conflict, which need to be resolved. (There are various tools to resolve conflicts, but I find simply editing the files often the easiest way.) You can repeat this as often as you want.

Now that you are ready to commit your work, your issue:

There is still a chance that between since the last git pull command someone has pushed a new commit. In that case a merge will occur in your history. This merge could have broken the build and/or some tests. It is good to verify if this the case and fix any problems.

Editted text on October 7, 2020

This months interesting links

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