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I ❤️ to build software. I sadly do not have a lot of time next to my daily work to spend on my side projects, so I have to be disciplined in where I invest time. I wish I could spend endless amounts of time on exploring new technologies, but sadly I simply do not have that time. In writing this is sometimes referred to as “to kill your darlings”.

It is December again and that means it is time for the Advent of Code. Due to my workload and family obligations I will probably not be able to get very far this year, but still I wanted to write a post about it.

This year I am using Java, together with my students. My goal is to write as modern as possible Java, which means using streams and new language constructs where possible.

My old laptop, now almost 6 years old, has seen it all. From conferences, to lectures, traveling to distant places and to the library. I did a lot of work on it during the writing of my thesis, and it is a victim to countless hours of compiler time.

Sadly the battery started to die. It got to the point that you can only use it shortly for heavier loads. Luckily, unlike certain hardware (looking at you Apple), it is easy to fix. All it needs is a new battery. So I found that ifixit had the right parts and a very useful kit with all the right tools to do the job.

Today the academic world is remembering Bastiaan Heeren, who passed away last week.

I spent the better time of a year working on my thesis, and before that I enjoyed lectures given by Bastiaan. He was a person with a great love for teaching, especially when you can get into the nitty gritty details of software quality and the benefits of functional programming.

I look back fondly on my time with Bastiaan. He was an open, warm, critical and encouraging human being. He had a great love for his family and work.

I recently came across Traefik. It is a reverse proxy built specifically for services in the cloud. I was searching for a convenient (up-to-date) way to expose my project using a reverse proxy within docker-compose. I used to use nginx for this, but it then requires a generator and an lets encrypt listener (so 3 containers). Traefik only requires a single container and allows you to label your docker containers to apply rules to them.

This is my first article in a series called Rock Solid Software. In it I explore different dimensions of software that does not simply break. You can write good software in any programming language, although some are more suited to a disciplined practice then others, Clojure is definitely in the relaxed space of discipline here.

Today I am exploring the use of Selmer templates in Clojure. If you have explored Biff at all you will know that all the UI logic works by sending Hiccup through a handler, which will turn into HTML through rum (specifically the wrap-render-rum middleware). If you provide a vector as a result for an endpoint, it will be converted to HTML.

Je hebt tijd gereserveerd om te gaan studeren en je volgt een ritueel om goed in jouw “Deep Work” modus te komen, dat studeren gaat echt goed lukken! Tijdens de colleges en in de lesmaterialen vind je allerlei links naar papers, websites, YouTube videos en haal je veel informatie uit boeken. Al deze bronnen zijn zeer waardevol en bij de eindopdracht zul je veel van deze bronnen weer moeten gebruiken om argumenten te onderbouwen of juist iets te ontkrachten. Hoe ga je dan om met die bronnen zonder dat je gek wordt van allerlei documentjes?

In mijn vorige artikel heb ik uitgelegd hoe je tijd kunt vinden om te studeren, de vraag is echter, is alle tijd hetzelfde? Het simpele antwoord is “nee”. Maar waarom niet, zul je vragen, en daarmee komen we op het onderwerp van dit artikel.

Cal Newport heeft een fantastisch boek geschreven, “Deep Work: Rules for Focused Success in a Distracted World”. In dit boek onderzoekt hij hoe je gefocust werkt en wat er voor nodig is om gefocust te blijven [1]. In het boek identificeert hij 2 soorten werk; “Deep Work” en “Shallow Work”. Deze concepten hebben voor mij de aanpak van mijn dagelijkse werk zelfs veranderd, maar dat is een verhaal voor een andere keer.

This is a Dutch artcile, there is also an English version.

Dus, jij hebt besloten om te gaan studeren? Misschien wil je jouw HBO- of Masterdiploma halen, of juist dat ene supertechnische certificaat bemachtigen. Het is geweldig dat je deze stap gaat zetten, maar zodra je begint, zul je vrij snel de vraag moeten beantwoorden waar je de tijd vandaan haalt.

Tijd is onze meest waardevolle, niet-hernieuwbare bron. Studeren vergt tijd – en niet zo’n klein beetje ook – dus wil je het natuurlijk goed doen. De meeste studies verwachten dat je wekelijks ergens tussen de 12 en 24 uur investeert om bij te blijven, en dat is flink wat! Als je nog niet studeert, probeer dan eens na te denken over welke dagen en momenten je die tijd kunt vrijmaken. Ga je minder uit eten of juist minder sporten? Vroeg opstaan in het weekend, of juist extra laat naar bed?

This is an English article, there is also a Dutch version.

So, you’ve decided to start studying? Maybe you want to earn your Bachelor or Master’s degree, or perhaps you’re aiming for that highly technical certificate. It’s great that you’re taking this step, but once you begin, you’ll quickly need to answer the question of where you’ll find the time.

Time is our most valuable, non-renewable resource. Studying requires time – and not just a little – so you naturally want to use it well. Most programs expect you to invest between 12 and 24 hours per week to keep up, and that’s quite a bit! If you’re not currently studying, try thinking about which days and times you could free up that time. Will you eat out less or exercise less? Get up early on weekends or stay up late?

So, on Thursday I defended my thesis in front of the graduation committee, and passed! This means that the work I have been doing for the last year comes to an end. From now on there are not long nights and weekends working on my thesis anymore.

Back in 2021 I started my journey of achieving a Master’s degree, first with a connecting program and then with the 2 year Master program. Even though I have been in computer science in some form for the last 30 years I still found it to be quite a learning experience.

So, today I have some news. I will be resigning as Ambassador for Hack The Box after our in-person meetup in June (2024). This means that I will be stepping down from organizing the monthly virtual and quarterly in-person Hack The Box meetups. Let me explain how I got to this decision.

The beginning

So, in 2019, I started out building a cyber security curriculum for NOVI Hogeschool. I had the ability to greenfield the courses and create something that is of value to students. In this curriculum I started using Hack The Box for exercises and training next to the regular classwork.

Last week I was a guest on the Cyber Cafe podcast by rootsec. It was a fun discussion on education and the current xz backdoor story. It is in the Dutch language. It is available on youtube and included below:

This post is just a small note for those of you who also run Microsoft Teams on Linux through their browser and now receive a note “your browser does not meet the requirements for the new Teams”. It turns out that the client is looking at the user-agent string to determine which browsers it accepts, and which not.

So, if you have the message, install an user-agent switcher and select a common browser on a common OS (from the MS perspective) and you will suddenly meet the requirements.

This is a longer form article. I is relevant as of February 18th 2023. If the circumstances of my environment changes I will try to update this article to reflect the situation. You can find the full source code of my dotfiles on Github.

I like consistency and simplicity. I do not like to use many different tools to do different things, I rather spend my time learning to use a few tools very well then to follow the hype on the latest trend of tools for something we have been doing forever.

It has been a little while. I have been swamped with work and the work on my thesis, leaving no room to finish the Advent of Code or much of anything else.

Yesterday I gave my practice presentation for my thesis. This means I am one more step closer to the finish line. During the day there were many interactions with fellow students. One of the topics has been the templates to use at Open Universiteit. So, I thought I would just create a repository of the templates that I use, so that anyone can learn from them.

The weekend generally is a place to find hard puzzles again, this time not so much. A simple quest to find the next number in a sequence with a fully written out algorithm to follow. They key here is to use recursion.

Somewhat suspicious of 2 easy days we end up at Day 8. A simple map to follow again, from one key follow the instructions until we hit ZZZ. Part 2 had us do it for several keys at once, with the goal to find the spot where they all converge. This can take forever, erhm, a long time.

So there has to be a math type solution to this problem. It turns out to be a Least Common Multiple problem. It is the smallest positive integer that is divisible by two or more numbers without leaving a remainder. To find the LCM of two or more numbers, you can use a method called prime factorization or a simpler approach involving multiples. We can also use the Greatest Common Divisor (GCD) to find the LCM.

Today we learned about CamelCards, a game of poker meant to play on the back of a camel. The most interesting part here was the parsing of the cards and figuring out how to properly rank them. Part 2 turned out to be as easy as tracking Jokers.

Day 6 turned out to be the easiest day in the range so far. A simple implementation of the algorithm was more than sufficient.

I later learned that it was a quadratic function. On the subreddit Deatranger999 said:

If you hold down the button for x seconds, then you will beat the distance if the quadratic x^2 - t x + d is at most 0, where t is the total time of the race and d is the distance you’d like to beat. So I just plugged each one into WolframAlpha, found the roots, and then calculated the number of integers between the two roots.