{"@attributes":{"version":"2.0"},"channel":{"title":"lewinb.net - Lewin Bormann on Lewin Bormann","link":"https:\/\/lewinb.net\/","description":"Recent content in lewinb.net - Lewin Bormann on Lewin Bormann","generator":"Hugo","language":"en-us","lastBuildDate":"Tue, 17 Mar 2026 18:59:26 +0100","item":[{"title":"See more on SkySee","link":"https:\/\/lewinb.net\/posts\/29_skysee_developed\/","pubDate":"Tue, 17 Mar 2026 18:59:26 +0100","guid":"https:\/\/lewinb.net\/posts\/29_skysee_developed\/","description":"

After I released the first version of SkySee<\/a> - see skysee.ch<\/a> - I quickly received\nfeedback, and also felt myself, the limits of a pure SHV number based tagging. To recap, Swiss glider pilots are\nobligated to put their Swiss paragliding\/delta association (SHV) membership number on the down-facing side of their\nglider, for accountability purposes. The original SkySee idea was to repurpose this number for sharing flight photos\namong pilots.<\/p>\n

However, depending on the perspective, in dynamic situations, or from far away, the letters can not always be read\neasily; especially on snapshots or videos with limited resolution. In addition, there are plans to replace the physical\nSHV number with an electronic identification system in the next few years: so the days of SHV number tagging would be\nlimited anyway.<\/p>"},{"title":"Building SkySee","link":"https:\/\/lewinb.net\/posts\/28_skysee\/","pubDate":"Fri, 06 Feb 2026 17:18:38 +0100","guid":"https:\/\/lewinb.net\/posts\/28_skysee\/","description":"

Context<\/h2>\n

In the past weeks, I’ve built a web application from the ground up, scratching an itch I’ve had for\na long time. Since fall 2024, I’ve been the proud owner of a Swiss paragliding license, and I’ve\nbeen making use of this privilege quite a bit (but not as much as I would have liked).<\/p>\n

My second-favorite part of a day going flying is the time spent in between flights. Whether that’s\ntalking to other pilots, hiking, eating lunch, or taking photos. This means I’ve ended up with a\nwhole lot of photos of other pilots: sometimes during the final leg before landing, or during their\ntake-off, and often enough even while in the air.<\/p>"},{"title":"News in uvco","link":"https:\/\/lewinb.net\/posts\/27_uvco_news\/","pubDate":"Sun, 07 Dec 2025 12:52:35 +0100","guid":"https:\/\/lewinb.net\/posts\/27_uvco_news\/","description":"

How time passes! This is already the third article discussing my uvco<\/a> library for\nasynchronous programming in C++ - the uvco tag<\/a> shows all past and future articles.<\/p>\n

The reason for this installment are several fundamental improvements I’ve implemented in recent weeks, turning the\nfledgling, sometimes unstable and hard to use uvco library discussed in those previous articles, into a more robust and\nscalable framework for almost-serious asynchronous programming in C++. In addition, several benchmarks have been\nimplemented to better quantify the throughput and latency numbers currently achievable with uvco.<\/p>"},{"title":"But what is a Quantum Control System?","link":"https:\/\/lewinb.net\/posts\/26_qcs\/","pubDate":"Tue, 21 Oct 2025 09:32:14 +0200","guid":"https:\/\/lewinb.net\/posts\/26_qcs\/","description":"

In my job at Zurich Instruments, I’m busy most days building software for a quantum control system<\/em> (QCS). And even\nthough that’s something very tangible for me, it’s often difficult to explain to folks outside of the field, and\nsometimes I struggle to describe precisely to other physicists what a QCS is or does.<\/p>\n

So first, for a working definition we use internally: A QCS is a system used in building quantum computers, specifically\nconcerned with controlling the individual qubits. Each qubit is a discrete physical system typically exhibiting two\nenergy states, and by coupling them to each other, quantum computations can be executed on the quantum computer. How\nspecifically that works is beyond this discussion (and also beyond me, if I’m honest). Oftentimes, the chip (if it is a\nchip) containing qubits is called the QPU<\/em>, or Quantum Processing Unit, in analogy to the CPU or GPU. But as I will\ndescribe further down, this term is not quite clear and can be used in a different way. Also note that despite having an\neducation in physics, I’m working on the QCS software<\/em> – I have many extremely competent colleagues with PhDs in\nquantum computing who are much better able to explain the finer aspects of quantum computing.<\/p>"},{"title":"Design of the uvco async library","link":"https:\/\/lewinb.net\/posts\/25_uvco_design\/","pubDate":"Tue, 30 Jul 2024 22:06:26 +0200","guid":"https:\/\/lewinb.net\/posts\/25_uvco_design\/","description":"

New article, discussing recent developments and improvements: News in uvco<\/a><\/center><\/strong><\/p>\n

I’ve already presented my “uvco” library in a previous post<\/a>. Here I want to go\ndeeper on the underlying design ideas and mechanics of using C++ coroutines to make using libuv a lot more ergonomic\nthan otherwise.<\/p>\n

The outcome is similar to e.g. Node.js concurrency - not surprising, because that’s still libuv’s main use case - or Python’s\nasyncio<\/code> library.<\/p>\n

Getting Started with C++ coroutines<\/h2>\n

When coroutines were first standardized, I was looking forward to using them. Having used Go before, I hoped that\nwriting concurrent and parallel code would finally become more accessible in C++. However, if you read references for\nC++ coroutines, you’ll notice that they never talk about concurrency at all. That was initially a bit difficult to\nunderstand, and I wasn’t quite sure what coroutines would be good for then.<\/p>"},{"title":"ELF Linking and Loading in Practice","link":"https:\/\/lewinb.net\/posts\/24_elf_linking_and_loading\/","pubDate":"Mon, 22 Apr 2024 19:28:54 +0200","guid":"https:\/\/lewinb.net\/posts\/24_elf_linking_and_loading\/","description":"

I’ve programmed in C and C++, later in Rust and OCaml, for more than 12 years now. One of the most interesting aspects\nto me were the operating system, how code interacts with it, and how code is run. Like most people, I followed the\ntypical journey: compile your first code using gcc -c hello.c<\/code>, then link it using gcc -o hello hello.o<\/code>, and finally\nrun it using .\/hello<\/code>. With libsocket<\/a> I published a library for both C and\nC++, facilitating using the sockets API on Unix systems - and as a library, I had to learn how to build a dynamic\nlibrary (shared object, SO), and how to link against it. I’ve had my fair share of linker errors, too, but one thing\nstood out to me: linking and loading are complex processes, but generally so reliable that they almost always work. And\nif they don’t it’s usually my own fault - a missing translation unit, or something similar.<\/p>"},{"title":"A simple Priority Queue in OCaml","link":"https:\/\/lewinb.net\/posts\/22_priorityqueue_ocaml\/","pubDate":"Sat, 30 Dec 2023 18:26:38 +0100","guid":"https:\/\/lewinb.net\/posts\/22_priorityqueue_ocaml\/","description":"

While working on some programming quiz in OCaml<\/a>, I needed to use a priority queue (or\nheap) in order to solve some graph traversal problem. However, unfortunately, OCaml doesn’t provide\nany sort of priority queue or heap in its standard library. And after a brief search I haven’t found\nany that satisfied me in terms of their interface.<\/p>\n

However, in I came across the idea to simply use a Set<\/code> keyed by (int * 'a)<\/code> where int<\/code> is the\npriority and 'a<\/code> the payload. That’s clever! The access complexity for the min (or max) element is\nnow log N<\/code> but that is still better than not having a proper heap. I also didn’t feel like writing\nmy own heap based on an array or a simple tree structure; making use of the well-known Base.Set<\/code>\nmodule seemed more attractive. I generally use Jane Street’s Base<\/code> and Core<\/code> all the time, as they\nare a bit more pleasant to use and more complete than the standard library.<\/p>"},{"title":"The uvco C++ async library","link":"https:\/\/lewinb.net\/posts\/21_uvco_asynchronous_library\/","pubDate":"Sun, 26 Nov 2023 23:37:20 +0100","guid":"https:\/\/lewinb.net\/posts\/21_uvco_asynchronous_library\/","description":"

Updated: May 7, 2024<\/em><\/p>\n

New article, going in depth on uvco: Design of the uvco async library<\/a><\/center><\/strong><\/p>\n

Since starting my new position at Zurich\nInstruments<\/a> I’ve worked a lot with the lovely kj<\/code>\nframework, in conjunction with capnproto RPC<\/a>. kj<\/code> is\nan asynchronous network programming library, and gained support for C++\ncoroutines in version\n1.0<\/a>. For this use\ncase, coroutines are great, simplify usage, and may even yield performance\nimprovements.<\/p>\n

To get a better understanding, I attempted my hand at writing a small coroutine\nframework driven by the libuv<\/a> event loop. While there were\nsome snags to be navigated, this turned out to be a great fit, and I quickly\nmanaged to map a good part of its functionality to a coroutine-based\nimplementation.<\/p>"},{"title":"Functional JSON Access","link":"https:\/\/lewinb.net\/posts\/20_functional_json_access\/","pubDate":"Sat, 26 Aug 2023 13:49:15 +0200","guid":"https:\/\/lewinb.net\/posts\/20_functional_json_access\/","description":"

While working on typst_of_jupyter<\/a>, I came across a very common problem: efficiently and\nreliably accessing nested JSON structures. This is an age-old problem that every programmer will have come across, and\nit’s easier in some languages – dynamically typed ones like Python or JavaScript – and more annoying in others.<\/p>\n

typst_of_jupyter is written in OCaml<\/a>, which – being statically typed – rather falls into the\nsecond category. In order to generate typst code for a Jupyter notebook, the JSON structure representing the notebook\nmust be processed. It is not a very complicated structure, but enough to be annoying to deal with in a plain way.<\/p>"},{"title":"Typst_of_jupyter: Better notebook PDFs","link":"https:\/\/lewinb.net\/posts\/19_typst_of_jupyter\/","pubDate":"Thu, 27 Jul 2023 00:30:02 +0200","guid":"https:\/\/lewinb.net\/posts\/19_typst_of_jupyter\/","description":"

If you have followed my posts (unlikely, given the visitor counts of my website), you have seen\none<\/a> or two<\/a> posts about\nTypst<\/a>, the new text-based typesetting system. I’ve already shown in a previous\npost<\/a> that Typst can be very useful as an intermediate language for\ngenerating PDFs.<\/p>\n

Disappointed by the various ways of exporting Jupyter notebooks<\/a> – printing from the browser, converting to LaTeX,\npandoc, etc. – I was looking for an approach that allows for archiving and sharing high-quality versions of Jupyter\nnotebooks preferably as PDF files. The idea to use Typst for generating such PDFs was obvious!<\/p>"},{"title":"Playing with OCaml Effects","link":"https:\/\/lewinb.net\/posts\/17_playing_with_ocaml_effects\/","pubDate":"Sun, 23 Jul 2023 15:40:04 +0200","guid":"https:\/\/lewinb.net\/posts\/17_playing_with_ocaml_effects\/","description":"

A few weeks ago I finally started seriously working with OCaml<\/a>, after having ignored it for a long\ntime. The main reason was the lack for multithreading, which I felt is essential these days (even though most code, of\ncourse, doesn’t make use of it.) But OCaml 5 was released a few months ago, and has removed this barrier – along with\nintroducing Effect handlers<\/em><\/a>, a smooth way for handling all kinds\nof ways to hack a program’s control flow.<\/p>"},{"title":"Foothills of Zug","link":"https:\/\/lewinb.net\/photos\/11_foothills\/","pubDate":"Fri, 21 Jul 2023 23:31:49 +0200","guid":"https:\/\/lewinb.net\/photos\/11_foothills\/","description":"

The “secret” to the most clich\u00e9 idyllic landscapes is to not look in the alpine regions, but in the foothills preceding\nthem. In this case, in the canton of Zug between Aegerisee and Raten pass (1080 m above sea level). With the farmers\nrushing to take in hay before the arriving rainstorm, the perfect scene was set.<\/p>\n

No more talk – the photos speak for themselves:<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n\n \n<\/a>\n

\n \n \n \n \n E 16-70mm F4 ZA OSS \n \n<\/i><\/center>\n\n\n\n\n\n\n\n\n\n\n\n\n\n \n<\/a>\n
\n \n \n \n \n E 16-70mm F4 ZA OSS \n \n<\/i><\/center>\n\n\n\n\n\n\n\n\n\n\n\n\n\n \n<\/a>\n
\n \n \n \n \n E 16-70mm F4 ZA OSS \n \n<\/i><\/center>\n\n\n\n\n\n\n\n\n\n\n\n\n\n \n<\/a>\n
\n \n \n \n (Location<\/a>) \n E 16-70mm F4 ZA OSS \n \n<\/i><\/center>\n\n\n\n\n\n\n\n\n\n\n\n\n\n \n<\/a>\n
\n \n \n \n (Location<\/a>) \n E 16-70mm F4 ZA OSS \n \n<\/i><\/center>\n\n\n\n\n\n\n\n\n\n\n\n\n\n \n<\/a>\n
\n \n \n \n (Location<\/a>) \n E 16-70mm F4 ZA OSS \n \n<\/i><\/center>\n\n\n\n\n\n\n\n\n\n\n\n\n\n \n<\/a>\n
\n \n \n \n (Location<\/a>) \n E 16-70mm F4 ZA OSS \n \n<\/i><\/center>\n\n\n\n\n\n\n\n\n\n\n\n\n\n \n<\/a>\n
\n \n \n \n (Location<\/a>) \n E 16-70mm F4 ZA OSS \n \n<\/i><\/center>\n\n\n\n\n\n\n\n\n\n\n\n\n\n \n<\/a>\n
\n Mount Rigi and Pilatus, near Lucerne.<\/b> \n \n \n (Location<\/a>) \n E 16-70mm F4 ZA OSS \n \n<\/i><\/center>\n\n\n\n\n\n\n\n\n\n\n\n\n\n \n<\/a>\n
\n \n \n \n (Location<\/a>) \n E 16-70mm F4 ZA OSS \n \n<\/i><\/center>\n\n\n\n\n\n\n\n\n\n\n\n\n\n \n<\/a>\n
\n Mount Rigi (on the right)<\/b> \n \n \n (Location<\/a>) \n E 16-70mm F4 ZA OSS \n \n<\/i><\/center>\n<\/p>"},{"title":"The Law of Lawyers","link":"https:\/\/lewinb.net\/posts\/16_law_of_lawyers\/","pubDate":"Sun, 18 Jun 2023 13:47:26 +0200","guid":"https:\/\/lewinb.net\/posts\/16_law_of_lawyers\/","description":"

Background<\/h2>\n

Over the past years, I’ve repeatedly seen articles claiming a looming shortage of lawyers:<\/p>\n