## return first

Let me introduce the “return first” method? Fear not, this is not a treatise on guard-clauses. What it is, is both a code design approach and a refactoring method. It starts with a simple question to ask yourself whenever you want to call a function:

Can I return first?

That’s supposed to be catchy, but it is probably not terribly enlightening. Let me demonstrate with an example. I’ll be using C++, but I dare say that this method can be used in all imperative languages.

void process_all(
std::vector<input_info_t>& input_list,
context_t const& context,
target_t const& target)
{
for (auto& each : input_list)
{
if (some_filter_applies(each, context))
{
hand_off_to(each, target);
continue;
}

process_one(each, context);
hand_off_to(each, target);
}
}


For the sake of this example, the three functions some_filter_applies, process_one and hand_off_to are immutable. Let us try to improve process_all by extracting a function:

void maybe_process_and_hand_off(
input_info_t& input,
context_t const& context,
target_t const& target)
{
if (some_filter_applies(input, context))
{
hand_off_to(input, target);
return;
}

process_one(input, context);
hand_off_to(input, target);
}

void process_all(
std::vector<input_info_t>& input_list,
context_t const& context,
target_t const& target)
{
for (auto& each : input_list)
{
maybe_process_and_hand_off(each, context, target);
}
}


So what do we have now:

1. 26 instead of 17 lines. 22 instead of 13 if we do not count lines with just braces, a 70% increase.
2. A pretty clumsy name for the function called in the loop. Can you do better?
3. We have to pass the target all the way to hand_off_to without really using it directly in maybe_process_and_hand_off.
4. The complexity is more or less the same.

So that was not great. So let us try to use return first and focus on hand_off_to. What if instead of calling hand_off_to, we just return first, and then do it? In this case, it’s pretty easy, since hand_off_to is a tail-call in each case:

void maybe_process(
input_info_t& input,
context_t const& context)
{
if (some_filter_applies(input, context))
{
return;
}

process_one(input, context);
}

void process_all(
std::vector<input_info_t>& input_list,
context_t const& context,
target_t const& target)
{
for (auto& each : input_list)
{
maybe_process(each, context);
hand_off_to(each, target);
}
}


Now we no longer have to pass target through a function that does not need it, which makes both the call site and the function declaration simpler. Now a few more other refactorings are available. Let’s assume some_filter_applies is pure and process_one only changes its input parameter, as the signatures suggest. We can use loop fission, and inline the function again:

void process_all(
std::vector<input_info_t>& input_list,
context_t const& context,
target_t const& target)
{
for (auto& each : input_list)
{
if (some_filter_applies(each, context))
{
continue;
}

process_one(each, context);
}
for (auto const& each : input_list)
{
hand_off_to(each, target);
}
}


“return first” actually works for all control structures, not just functions. So in this case we returned from the first loop before starting to call hand_off_to multiple times. Often times, the code will not be as easy to refactor, because there is actually some data flowing between the function we’re in and the one we’re calling. The simple solution then is to pack all the parameters into a struct and return that, aka using data as the interface instead.

void hand_off_individually(
std::vector<input_info_t>& input_list)
{
for (auto& each : input_list)
{
auto target = compute_target(each);
if (!target.valid())
continue;

hand_off_to(each, target);
}
}


That be turned into this:

void hand_off_individually(
std::vector<input_info_t> const& input_list)
{
struct targeted
{
input_info_t info;
target_t target;
};
std::vector<targeted> valid;
for (auto const& each : input_list)
{
auto target = compute_target(each);
if (!target.valid())
continue;
valid.push_back({each, target});
}

for (auto const& each : valid)
{
hand_off_to(each.info, each.target);
}
}


This is definitely longer, and probably not worth the hassle for this contrived example – this is more to show how to do it, not that is is effective.

# Evaluation

In real programs, this applying “return first” is often worthwhile. It makes the code flow “wider instead of deeper”, which is often easier to follow, especially if you try to debug or measure/profile your code. It is also a gold-recipe to enable batching, which is curcial whenever you’re dealing with latency, e.g. when using RAM or building web requests. Have you tried this technique before? Do you, maybe, know it by another name? Do tell!

## Key ingredients for the home office

Since March 2020, we transformed from an “on-site” company to a remote company, not particularly because we wanted to, but because the corona pandemic forced us to. Our office is not suitable to ensure transmission safety, so I decided that work from home is the lesser problem. When I say “transform” and “decided”, please bear in mind that these are retrospect notions. The decision was made at Monday, March 16th 2020 and the transformation happened in the next two days.

But there is a real difference between being operable and fully equipped for the situation. We were operable in the remote situation within 48 hours. But we still work on improving our equipment to match the situation that seems to linger a lot longer than initially anticipated. This blog post tries to summarize what we’ve learned since March 2020 in regards to equipping home office workplaces past the makeshift phase.

## The fundamentals

The most fundamental ingredients of any office workplace are the table and the chair. If any of those lack in necessary ergonomic features, your comfort will never be the same as in the office (provided that your equipment there is adequate). And this constant discomfort will permeat everything you do.

The chair was easier to detect because it shows up in the video calls, it is part of the “zoom room”. Still, it took some time to order new chairs or transport existing office chairs to the home offices. If you experience back pain or mechanically induced headaches, review your chair thoroughly.

The table was more tricky, because it is typically invisible during video calls. My approach was to retrieve a photo of every home office space and talk about the possible improvements. During these talks, we came up with two solution categories that I want to present.

## The notebook workplace

We all had work notebooks as secondary computers before the pandemic. So it was not a problem to start with working from home on that notebook, we’ve done it before. But if all you do is to work directly at a notebook, you might have the best chair and table, your body posture will be suboptimal. We equipped the notebook-based workplaces with the following extras:

• An external keyboard
• An external computer mouse
• One (or better: two) additional monitors
• A matching docking station, at least to connect to the monitors
• A notebook riser stand

The last item, the notebook riser stand, was the game changer when it came to multi-monitoring (two or three monitors). It elevates your notebook to the same height as the other displays and might even change its angle. This transforms your notebook from being the CPU unit with cumbersome monitor to a secondary monitor with a CPU. The riser stand doesn’t cost much (if you don’t go overboard with its design) and provides you with more table space and improved displays.

## The existing computer workplace

Because we are software developers, we mostly have a very decent computer already fully equipped at home. The only problem: The computer is for private tasks and should stay that way. We want to separate our work environment from our leisure environment as much as possible. But several developers wanted to use their usual “battlestation” for home office work, too.

In this case, we bought a lavish SSD as an additional boot drive for the home PC. This separates the work operating system from the leisure drive as much as the notebook approach. And the existing hardware can be used for both timeslots, much to the comfort of the developer.

## The video conference equipment

But regardless of your approach (notebook or existing computer), there are still some things missing that improve the quality of work of yourself and your colleagues tremendously:

• A good headset, preferably with top-notch comfort and active noise cancelling (ANC)
• An at least decent webcam

Most notebooks provide a mediocre webcam and some low quality microphone. Do yourself (and your communication partners) a favor and invest in a good microphone. Oftentimes, it is coupled with good headphones. The difference between a good audio setup and an echo-prone makeshift solution is the deciding factor when essentially all communication with your colleagues go through this channel.

The webcam is not as essential as the audio equipment, because it “only” affects your communication partners, but it adds a nice touch to your other equipment. You don’t have to go overboard on it, a model for one hundred euros is already an improvement.

## The bottleneck

One thing that can really invalidate most of the other improvements is a small internet connection. This is probably to hardest thing to fix in a timely manner, but give it some thoughts. If your internet connection is too slow for your daily work and communication pattern, it will be a constant annoyance. Just because it takes some time to improve doesn’t mean you shouldn’t try.

We will probably remain in this situation long enough to still reap the profit of our effort. And even if not (at least we can hope), nobody ever complained about an internet connection that is a bit oversized.

## TL;DR

If you didn’t read the article, here are the major take-away points neatly summarized:

• Ergonomic chair and table
• Notebook with external keyboard, mouse and monitor
• Notebook riser stand
• SSD for dual boot systems
• External webcam

If you miss an item from this list for your home office, give it a thought. And if you plan to only think about one item, think about your chair first.

What are your experiences with working from home? What accessory makes your work life better? Give us a hint by writing a comment below. Thank you!

## Windows 10 quality of life features

Starting with Windows 10 Microsoft switched from big-bang releases of its operating system to so called rolling releases: They release new features and improvements in regular intervals – once or twice a year – without changing the product name.

The great thing is that users get the improvements made by Microsofts engineers much sooner than in the past where you had to wait several years for a big “service pack” to arrive or even a new major release of Windows like 2000, XP, Vista, 7, 8, 8.1 and finally 10 (I am leaving out the dark times on purpose 😉).

The bad thing is that it is harder to see what version or release you are running. Of course there is a (less visible) name for every Windows release. This version or codename sometimes gets mentioned on support pages or in blog posts because functionality of Window 10 can change significantly between these rolling feature updates. And sometimes you may run some app or tool that tells you need Windows 10 2004 or higher.

## What version of Window 10 am I running?

I know of two simple ways to find out what version of Windows 10 you are running currently:

1. Running the tool winver
2. Opening the Settings -> System -> Info page

## Why does it matter?

Another downside is that users often are not aware of new stuff added to their operating system. And Microsoft does an awful job promoting the changes and improvements!

Of course there are announcements about the big things after upgrading your operating system to the next feature level. And Microsoft uses these for marketing its own apps and services. They slap you their new Edge-browser in the face on every occasion and try to trick you in creating a Microsoft account. It is absolutely not obvious how to use Windows without a Microsoft account like the decades before. Skip the process here, continue without and risk your live…

On the other hand they really improve their software and slowly but steadily round the rough edges of their system. The UIs for environment variables are finally quite usable.

Now back to the main theme of the post: There are some hidden gems built into Windows 10 that I learned of only lately and I think are vastly underadvertised – unlike Microsoft’s marketing of their big products.

## Built-in screen recorder

Ok, many gamers may know it because it Windows briefly displays the shortcut Win+G when starting a game. It is not only usable for games but you can record any window, capture application sounds and record your voice. You can easily record your own screencasts and video tutorials using this built-in solution.

## Built-in clipboard manager

How often did you wish to be able copy multiple items and choose one of the last few copied elements when pasting? While such clipboard managers have been around for a long time and sometimes provide tons of useful features Windows 10 has a simple one built-in. Just press Win+V instead of Ctrl+V to paste your clipboard entry and you will get a list of the copied items to choose from.

## Built-in screenshot/snipping tool

Many people may know the old way of making screenshots using the oddly labeled PrtScr-key (sometimes also PrntScrn or simply Print), opening a painting application like MS paint and pasting the image using Ctrl+V. Well, Microsoft improved this workflow a lot by including a snipping tool that you can activate using Win+Shift+S. This tool lets you select either a rectangular or free-form region, a window or an entire screen to capture. After doing that you get a notification allowing you to make modifications to the capture and save it to disk.

## On-screen emoji-keyboard

Just a little helper in these modern social media times is the on-screen emoji-keyboard. Using Win+. you can activate it, browse tons of common emojis and enter them into you messages and texts 🐱‍🏍🤘.

## Windows Terminal

Ok, this last but not least one is not (yet) built-in and mostly interesting for developers and power users. Nevertheless, I think it is noteworthy that Microsoft finally built a capable terminal application with modern features like multiple tabs, full unicode and font support, customizable background with blur and the ability to host different shells like the old and trusted command prompt CMD, the newer PowerShell and WSL. You can find it in the Microsoft store for free.

## Conclusion

While releases of Windows 10 are more subtle than past new Windows releases many things change both under the hood and user visible. Every once in a while something you missed for years or installed third-party tools for may be added without you knowing. That’s another reason why talking to colleagues and friends and practices like pair-programming and brown-bag meetings are so valuable for sharing knowledge and experience.

I hope there is something for you in my findings of hidden windows gems. If you have some Windows 10 features you discovered and really like, feel free to leave them in the comments. I will gladly try them out!

Every one of us has started somewhere. By telling you what my first computer was, I also convey a lot about the place and time my journey in IT started. For many of my fellows, it was a Commodore C64 or an Atari 500. But even if I don’t tell you about my first machine, there is a simple “magic spell” that you can cast to at least get a hint about the decade my first working days started, 15 years after my first contact with computers.

The spell is just one word: “container”. What a container is and how to use it is bound to the decades. Let me guide you through some typical answers.

If you entered the industry around the year 2000, a container was a big chunk of software that you preferably installed on an even bigger machine, the infamous “application server”. The container, or “servlet container”, “application container”, or, if you were with the right folks, “enterprise bean container” (in short: EJB-Container) was the central hub to host all of your web applications. If you deployed your application into the container, it handled the rest, like unpacking the web archive, providing resources and publishing to the internet. Typical names of containers were Tomcat, Jetty, JBoss or WildFly. You can probably see them around even today, because the concept itself is appealing. Some aspects of it inevitably lead to problems, though. Resource management was a big topic. Your application wasn’t expected to care for a database connection, a logging context or, sometimes, even security features, because the container provided those things to it. As you can probably imagine, that left your application crippled and unable to function outside a container.

So if you onboarded more than ten years ago, your first thoughts reacting to the word “container” will be “big machine”, “slow startup” and “logging framework”. There cannot reasonably be more than one container per machine. Maintaining a cluster of containers would be the work of luminaries. Being asked to start a container on your developer machine is a dreadful endeavour. “Booting the container” is a reason to visit the coffee machine.

But if you started your career less than ten years ago, your reaction to the word “container” will be different. Starting in 2013, a technology named “Docker” reinvented an old practice to isolate processes and package them into a transport format. Simplified enough, a container is just the RAM-based projection of an application image. You boot a container by loading the image into RAM. That’s some of the fastest things you can do on a computer (not really, but it fits the story better). Even better, because each container ideally contains just one small application or part of it, you don’t boot one container per machine, you can run dozens at the same time. Each container brings everything it needs with it and only relies on three common external resources being provided: Networking, persistent storage and a facility to dump logging output.

It is good practice to partition your application into several containers of the post-2010 kind. It is good practice to have them talk to each other over network, either real or simulated. The lines between actual computers get blurry real fast with this kind of containering.

As a youngster, your first thoughts reacting to the word “container” will be “just one?”, “scale up” and “log output management”. You see an opportunity to maintain a cluster of containers. Being asked to start a container on your developer machine is a no-brainer. “Booting the container” is a reason to automate your container infrastructure.

The reactions to the word “container” are very different, based on socialization period. In the old days, pre-2010 containers were boss fight adversaries. Nowadays, post-2010 containers are helpful spirits that just need to be controlled.

What better way to control the helpful spirits but to deploy them to an environment that handles unpacking, wiring, providing resources and publishing to the internet? Your application isn’t expected to care for topics like scalability, cluster robustness or load balancing. The environment, your container cluster platform, handles those things for you. There can only be one cluster platform per cloud. Being asked to start a cluster platform on your developer machine – well, that’s just not possible, sorry. Best we can do is a minified version of it. Our applications tend to function poorly outside a cluster platform.

As you hopefully can see, developers of all decades crave a thing they tend to call “container” that they can throw their software into to have it perform well without all the hassle of operations. But as soon as they give away responsibility for the environment, they also give away the possibility of comfortable “developer machine” operations. The goal is the same, just the technicality what exactly a “container” happens to be changes over time.

## Three programming languages the world isn’t ready for yet

The year 2020 is coming to an end and we can finally relax a bit. In order to lighten up your mood, this blog entry is comprised entirely of humor, satire and plain silliness. Nothing in it has any resemblance with reality and you should not try any of this at work. But if, for whatever reason, you find something useful in here and go to revolutionize the world of software development, remember that we’ve called it first.

There are many programming languages for all sorts of purposes. If you’ve developed software for some decades, you saw them appear, getting useful and being forgotten over the span of time. But what will the future bring? Here are the descriptions of three programming languages that have their purpose, but the world is not ready for them. They aren’t even invented yet!

## A programming language for long-lived projects

Most of today’s world source code is categorized as “legacy code”. This degatory term describes code that is old, unwieldy or just too clever for current programmers. Typical programming languages that have lots of legacy code include Cobol, C and Java. Most programmers don’t associate themselves with that code. It’s “other people’s” code. But there is one programming language that not only embraces the notion of “legacy code”, but in fact imposes it. This programming language is “Legacy”, the most productive one to produce heaps and heaps of, well, legacy code in short manners of time.

An unique feature of Legacy is that the code can be written at nearly the speed of thought, but is impossible to decipher even minutes later. A typical Legacy project doesn’t employ version control to differentiate between new and old code, but line numbers: Lower numbers indicate older code, while higher numbers are written more recently. To really drive this point home, every line of code needs to start with its line number, just like the good old BASIC did. An useful convention in Legacy is to choose the line number based on your current timestamp like 20201221181736 (the moment this text got written). Modern Legacy IDEs do this automatically for you.

(A cool but seldom used syntax feature that is based on the timestamp convention is the time-relative jump: You can address your jump target by absolute or relative line number, but even cooler is the relative amount of time: “jump -3d” resumes code execution at the line you wrote three days ago. Just remember: “jump +3d” is equivalent to undefined behaviour for most practical use cases. Only Legacy wizards can pull the “just-in-time jump” off in a useful manner.)

The most pressing issue about Legacy are its third-party dependencies: There are none. All dependencies are second-party dependencies, meaning they are much more involved in your project as usual. In order to compile or deploy a Legacy project, you need to have the exact version, down to the patch and oh-crap-i-forgot-hotfix number, of

• the Legacy SDK
• the compiler
• the IDE
• the Legacy runtime

The last point might be surprising, but given the different versions of Unicode and even UTF-8, the Legacy ecosystem has chosen to follow the ideal of Python that dictates the indentation, but redirect it to the parts outlined above. You don’t get to choose the compiler version, the compiler version chooses you, based on your Unicode level. By the way, indentation is a no-brainer in Legacy: Each line starts with the line number, that is enough indentation already.

If you want to deploy a Legacy project to a production server, you need, by the rules above, the exact machine with a perfect replication of all installations for development. Because this is a painful endeavour, most developers have adopted the best practice of “one machine per project” and develop directly on the production server. Most of the time, this is a surprisingly powerful machine, making programming even more faster (remember, the goal is to produce the most amount of code in the least time). It also shortens the delivery pipeline length and facilitates communication between business and development departments, even if not of the pleasant type.

A curiosity that novice Legacy programmers often don’t grok at first is the IMPOSE keyword. It is a variant of the IMPORT functionality of other languages, but doesn’t extend the capabilities of your code. Instead, it limits the ability of the developers in this project by the given imposition. A typical example would be the line

IMPOSE variable name length <= 3

That, as you can read in clear text, limits your variable names to three characters or less. You can often find Legacy code with variable names like “usr” instead of “user”, “pwd” instead of “password” and “idx” instead of “index”. They all follow the imposition above, increase your typing speed and speed up the compilation, which counts as a triple win.

So, if you want to impress your customer with huge amounts of important looking code and build a certain reputation among peers, Legacy might be your new favorite language. And if anybody calls your work result “legacy code” in the future, you should feel validated and proud.

## A programming language for mission-critical software

Software written for high-stake contexts like flight control, medical supervision and power plant management needs to meet extreme requirements in regard of correctness, robustness and resilience. Most mainstream programming languages have reacted by providing additional complexity to address the situation. For example, the demand for correct software has lead to the rise of testing frameworks that introduce additional syntax and require additional source code that is, by definition, untested in itself.

This is the problem the inventors of “Untested” try to solve. By writing your code in “Untested”, you can forgo all the extra effort of trying to prove it right. Untested code is, by definition, good enough without test. Remember the definition of Michael Feathers?

To me, legacy code is simply code without tests.

Michael Feathers in his book “Working Effectively with Legacy Code”

If you are ok with “Legacy”, you probably also enjoy “Untested”. The language makes it impossible to write tests for your code, so you can fend off the demand for them more easily. Your boss cannot ask for things that are impossible to do.

One interesting way in which “Untested” wards off calls from test routines is to couple every statement with a side effect in the hardware (oftentimes the TRAP flag on the CPU is flipped). Most programmers in traditional languages find those lines not testable and try to factor them away in order to test the rest. Untested factors away the rest. You don’t need to feel guilty about your lacking test coverage – it’s a feature, not a bug.

If your boss asks if a certain module is thorougly tested, you can respond “yes” in good faith. It’s tested in the best manner possible with “Untested”. If you need to give an overview of your system, you can write “Untested” beside every module and your reviewers will accept it as accurate.

Oh, the problem of long and tedious code reviews are taken into account, too. Because “Untested” code is just “Legacy” code (see Michael Feather’s definition above), it is impossible to read and understand with the exception of the developer machine (aka production server). If a thing is impossible to do, why even start trying? This will give you more time to produce “Untested” code.

And if problems arise in production? Well, you are already on the machine, so you can just hotfix it. Nobody can blame you, you’ve stated again and again that it’s untested code.

By the way: “Hotfix” is another promising programming language worth speaking about, but that would go beyond the scope of this blog entry. Might add it later, though.

## A programming language for non-programmers

The central tragedy of software development is that the people that CAN program don’t know what they SHOULD program and the people that know exactly what SHOULD be programmed CANNOT do it. The latter group is mostly managers and people with million-dollar ideas.

The new kid on the programming language block tries to solve this problem by utilizing state-of-the-art artificial intelligence in the compiler AND the runtime. We are talking, of course, about “Straightforward”. It’s a programming language with a natural syntax that’s so easy and lenient, you can call it, well – you probably get the joke by now.

Remember the last time a stunned manager tried to explain the new feature to you and, when you came up with an estimate encompassing weeks for the implementation, shouted out “but it’s straightforward!”. He talked about his preferred programming language and you probably misunderstood him again.

“Straightforward” is so popular with the business folks because the compiler is in the “do what I mean” category of compilers. By using natural language recognition, it infers your most probable meaning of the code, looks it up on the internet and translates it into machine code. The first versions used sites like stackoverflow.com for the translation step, but that didn’t work out, because the site is filled by developers, not business people. Newer versions just access the cloud and find the answer there.

The machine code of “Straightforward” is not actual binary code, but an intermediate representation, much like Java’s bytecode, but for non-technical concepts. Because these concepts are subject of interpretation and the zeitgeist, they are really interpreted again at execution time by another artificial intelligence. This approach might be a bit demanding with processing power, but that’s just a financial problem. The big advantage is that code like “Make the colors more lively!” is both compilable and executable and yields the correct results regarding the current fashion every time. Your color scheme doesn’t age as fast or virtually not at all with this straightforward code.

The only problem that prohibits widespread adoption of “Straightforward” in the business right now is the unsolved equation:

This is a fundamental theoretical problem in the field of management, much like P = NP in computer science. The race has already started, whoever solves his equation first gets the prize. It is rumored that quantum computing is the key to both. But I suspect that if quantum computing is available for everyday use, other programming languages like “ASAP” will take over the market.

I hope this blog post has entertained (and maybe inspired) you. Now, it’s your turn. What is the programming language you always wanted to use? Be silly, be creative, be vocal. Write a comment below and tell us!

## React for the algebra enthusiast – Part 2

In Part 1, I explained how algebra can shed some light on a quite restricted class of react-apps. Today, I will lift one of the restrictions. This step needs a new kind of algebraic structure:

## Categories

Category theory is a large branch of pure mathematics, with many facets and applications. Most of the latter are internal to pure mathematics. Since I have a very special application in mind, I will give you a definition which is less general than the most common ones.

Categories can be thought of as generalized monoids. At the same time, a Category is a labelled, directed multigraph with some extra structure. Here is a picture of a labelled directed multigraph – its nodes are labelled with upper case letters and its edges are labelled with lower case letters:

If such a graph happens to be a category, the nodes are called objects and the edges morphisms. The idea is, that the objects are changed or morphed into other objects by the morphisms. We will write $h:A\to B$ for a morphism from object $A$ to object $B$.

But I said something about extra structure and that categories generalize monoids. This extra structure is essentially a monoid structure on the morphisms of a category, except that there is a unit for each object called identity and the operation “$\_\circ\_$” can only be applied to morphisms, if they form “a line”. For example, if we have morphisms like k and i in the picture below, in a category, there will be a new morphism “$k\circ i$“:

Note that “$i$” is on the right in “$k\circ i$” but it is the first morphism if you follow the direction indicated by the arrows. This comes from function composition in mathematics, which suffers from the same weirdness by some historical accident. For now that just means that chains of morphisms have to be read from right to left to make sense of them.

For the indentities and the operation “$\_\circ\_$“, we can ask for the same laws to hold as in a monoid, which will complete the definition of a category:

## Definition (not as general as it could be…)

A category consists of the following data:

• A set of objects A,B,…
• A set of morphisms $f : A_1\to B_1, g:A_2\to B_2,\dots$
• An operation “$\_\circ\_$” which for all (consecutive) pairs of morphisms $f:A\to B$ and $g:B\to C$ returns a morphism $g \circ f : A \to C$
• For any object a morphism $\mathrm{id}_A : A\to A$

Such that the following laws hold:

• $\_\circ\_$ ” is associative: For all morphisms $f : A \to B$, $g : B\to C$ and $h : C\to D$, we have: $h \circ (g \circ f) = (h \circ g) \circ f$
• The identities are left and right neutral: For all morphisms $f: A\to B$ we have: $f \circ \mathrm{id}_A=\mathrm{id}_B \circ f$

## Examples

Before we go to our example of interest, let us look at some examples:

• Any monoid is a category with one object O and for each element m of the monoid a morphism $m:O\to O$. “$m\circ n$” is defined to be $m\cdot n$.
• The graph below can be extended to a category by adding the morhpisms $ef: B\to B, fe: A\to A, efe: A\to B, fef: B\to A, \dots$ and an identity for $A$ and $B$. The operation “$\_\circ\_$” is defined as juxtaposition, where we treat the identities as empty sequences. So for example, $ef\circ efe$ is $efefe: A\to B$.
• More generally: Let $G$ be a labelled directed graph with edges $e_1,\dots,e_r$ and nodes $n_1,\dots,n_l$. Then there is a category $C_G$ with objects $n_1,\dots,n_l$ and morphisms all sequences of consectutive edges – including the empty sequence for any node.

## Action Categories

So let’s generalize Part 1 with our new tool. Our new scope are react-apps, which have actions without parameters, but now, action can not neccessarily be applied in any order. If an action can be fired, may now depend on the state of the app.

The smallest example I can think of, where we can see whats new, is an app with two states, let’s call them ON and OFF and two actions, let’s say SWITCH_ON and SWITCH_OFF:

Let us also say, that the action SWITCH_ON can only be fired in state OFF and SWITCH_OFF only in state ON. The category for that graph has as its morphims the possible sequences of actions. Now, if we follow the path of part 1, the obvious next step is to say that SWITCH_ON after SWITCH_OFF (and the other way around) is the same as the empty action-sequence — which leads us to…

## Quotients

We made a pretty hefty generalization from monoids to categories, but the theory for quotients remains essentially the same. As we defined equivalence relations on the elements of a monoid, we can define equivalence relations on the morphisms of a category. As last time, this is problematic in general, but turns out to just work if we replace sequences of morphisms in the action category with matching source and target.

So in the example above, it is ok to say that SWITCH_ON SWITCH_OFF is the empty sequence on ON and SWITCH_OFF SWITCH_ON is the empty sequence on OFF (keep in mind that the first action to be executed is on the right). Then any action sequence can be reduced to simply SWITCH_ON, SWITCH_OFF or an empty sequence (not the empty sequence, because we have two of them with different source and target). And in this case, the quotient category will be what we drew above, but as a category.

Of course, this is not an example where any high-powered math is needed to get any insights. So far, these posts where just about understanding how the math works. For the next part of this series, my plan is to show how existing tools can be used to calculate larger examples.

## 3 good uses for the C++ preprocessor in 2020

As this weird year, 2020, comes to a close, I noticed that I am still using the preprocessor in my C++ programs. And not just for #includes which might, at last, slowly fade away with C++20’s modules. The preprocessor’s got a pretty bad rep, and new C++ programmers are usually taught to stay as far away as possible. Justifiably so – some things, like the dreaded X-Macros really should go the way of the dinosaurs.

But there are still some good uses left in the thing, and here’s my top 3 of those:

# 0. Commenting out big-chunks of code

I’ve often seen people comment out big parts of code with block comments: /* this is not active */. However, that will only work as long as the code does not contain any other block comments, let alone a stray */ in a string. A great alternative is to use the preprocessor:

#if 0
auto i_do_not_want_to_compile_this() -> auto
{
std::vector<std::deque<std::mutex>> baz{};
return baz;
}
#endif


This can easiely by wrapped multiple times around bigger parts of code, which is very helpful when refactoring large chunks of legacy code. It can very easiely be toggled on and off while in this state. And the IDE will usually still show a dimmed version of syntax highlighting in the disabled region.

# 1. Conditionally throw away “cross-cutting” concerns

Some parts of aspects of programs can be “cross-cutting”, which means they cannot easiely be separated from the rest of the code-base by putting them in a separate module. The most prominent example is probably logging. While you can typically modularize the actual implementation, the actual log calls will be all over your code. Another of those concerns is “profiling”. This is also something that you typically want to take out of your application when deploying it, because users will rarely profile the end-product. Again, the preprocessor comes to the rescue. For example, in the excellent Optick, most of the code you insert is actually macros that can be completely eliminated with a simple compile-time switch. Consider this “tag” that add some additional metric to your profile:

OPTICK_TAG("CoolMetric", compute_cool_metric());


When Optick is turned off via the aforementioned compile-time switch, compute_cool_metric() is never called. The call is not even compiled. Just turning Optick off will completely remove it from your source. Now this can be potentially dangerous, if the function has a side effect, but you wouldn’t do that anyways, would you?

# 2. Making forward declarations more visible

Presumably owing to its history as a continuously-evolved language, C++ has a very limited set of reserved keywords, often avoiding to introduce keywords to not interfere with any working software out there. Do not get me wrong, that is a great reason. But because of this, some language constructs can sometimes be a bit cryptic, for example forward declarations: class will_be_defined;. If you ever worked with a big, old or big and old code-base with lots of those, you probably know that maintaining them can be a bit of a chore and prone to error. So I think it is a great idea to at least make them more visible with your own macro “KEYWORD”:

#define FORWARD_DECL(x) class x

FORWARD_DECL(will_be_defined);


That FORWARD_DECL immediatly stands out visually and helps me keep track of those subtle declarations.

## Grammar as a leaky abstraction

Internationalisation, or i18n for short, is the process of making the user interface of a program ready for translation into multiple languages. This usually means to factor out texts from the program source code into separate files, often called translation bundles. These files have a key-value structure. The program code then only refers to keys that are resolved into the actual texts from the translation bundle for the selected target language.

Here’s a simple example of two translation bundles, one for English and one for German:

# translations_en.properties
quit_confirm_message=Do you really want to quit?
yes_option=Yes
no_option=No
# translations_de.properties
quit_confirm_message=Wollen Sie die Anwendung wirklich beenden?
yes_option=Ja
no_option=Nein

The actual source code might look like this:

var answer = showDialog(
t("quit_confirm_message"),
t("yes_option"),
t("no_option")
);

Here the function t looks up the key in the currently active translation bundle and returns the translated message as a string.

#### How not to do it

Last month I discovered an amusing attempt at internationalisation in a third-party code base. It looked similar to this:

# translations_en.properties
a=A
an=An
is=is
not=not
available=available
article=article
# translations_de.properties
a=Ein
an=Ein
is=ist
not=nicht
available=verfügbar
article=Artikel

These translation keys were used like this:

"${t('an')}${t('article')} ${t('is')}${available ? '' : t('not')} ${t('available')}." to produce messages like "An article is available." "An article is not available." … or in German: "Ein Artikel ist verfügbar." "Ein Artikel ist nicht verfügbar." Why is this a clumsy attempt at internationalisation? Because it uses single words as translation units, and it relies on the fact that English and German have the same sentence structure in this particular case. In general, of course, languages do not have the same sentence structure, not even related languages like English and German. The author of the code also introduced separate translation keys for “a” and “an”. The German translation for both keys was “ein”. The author was lucky so far that all texts with “a” or “an” in this particular program translated to “ein” in German, not “eine”, “einen”, “einem”, “einer”, or “eines”. #### How to do it So what would be the correct way to do it? The internationalisation should have looked like this: # translations_en.properties article_available=An article is available. article_not_available=An article is not available. # translations_de.properties article_available=Ein Artikel ist verfügbar. article_not_available=Ein Artikel ist nicht verfügbar. available ? t("article_available") : t("article_not_available") By using whole phrases and sentences as translation units the translations into various languages have the freedom to use their own word orders and grammatical structures. ## Keeping in touch with your pipeline Jenkins jobs We are using continuous integration (CI) at the Softwareschneiderei for many years now. Our CI platform of choice is historically Jenkins which was called Hudson back in the day. Things moved on since then and the integration with GitLab got a lot better with the advent of multibranch pipeline jobs. This kind of job allows you to automatically build branches and merge requests within the same job and keep the builds separate. Another cool feature of Jenkins is the job configuration as code, defined in Jenkinsfile and used in pipeline jobs. That way it is easy to create and maintain a job configuration alongside your project’s source code inside your repository. No need anymore to click through pages of web UIs to configure your job. That way you also get the complete job configuration change history as additional benefits. I prefer using scripted instead of declarative pipelines for Jenkinsfiles because they give me more control, freedom and power. But like always, this power and flexiblity comes at a price… ## Sending out build notifications In my case I wanted to always send out build notification regardless of the job result. This is quite easy if you have plugins like the Mattermost Notification Plugin or one of the mail plugins. Since our pipeline script consists of Groovy code this seems quite straightforward: Put the notification code into a try-finally-block: node { try { stage ('Checkout and build') { checkout scm // Do something to build our project } // Maybe some additional stages like testing, code-analysis, packaging and deployment } finally { stage ('Notify') { mattermostSend "${env.JOB_NAME} - ${currentBuild.displayName} finished with Status [${currentBuild.currentResult}] (<${env.BUILD_URL}|Open>)" } } }  Unfortunately, this pipeline script will always return SUCCESS as the build result! Even if someone aborts the job execution or a stage in the try-block fails… ## Managing build status So the seasoned programmer probably already knows the fix: Setting the build result in appropriate catch-blocks: node { try { stage ('Checkout and build') { checkout scm // Do something to build our project } // Maybe some additional stages like testing, code-analysis, packaging and deployment } catch (Exception e) { if (e in org.jenkinsci.plugins.workflow.steps.FlowInterruptedException) { currentBuild.result = 'ABORTED' } else { echo "Exception:${e.class}, message: ${e.message}" currentBuild.result = 'FAILURE' } } finally { stage ('Notify') { mattermostSend "${env.JOB_NAME} - ${currentBuild.displayName} finished with Status [${currentBuild.currentResult}] (<\${env.BUILD_URL}|Open>)"
}
}
}


You can control the granularity and the exceptions thrown by your build steps at will and implement exactly the status reporting that you want. The available statuses are defined in hudson.model.Result, so feel free to realize your own build status management to best fit your project.

## From multiplayer Pac-Man to a twenty year old company

This blog post does not contain big insights. It’s just the story of the very first days of our company which happens to celebrate its 20th anniversary this month. And because most stories begins a lot earlier than when the narrator begins to tell them, I’ll try to tell this one from the start.

It starts with an eight-year old boy that has access to his very first personal computer, a Tandon 8088 with 8 MHz. Just to put this glorified pocket calculator in today’s perspective: A basic arduino board has more power. But back in the days, this personal computer was a magical tool that could act as all kinds of things, including a gaming machine. One of the first games on this machine was Pac-Man, in 80×25 character ASCII “graphics” and without any scoreboard or competitive element. It was strictly single player and the computer-controlled ghosts acted strictly by their algorithms, so it became a repetitive chore rather soon. The boy would play the usual route, add some new steps at the end and watch the ghosts react. After some time, the boy could predict the ghosts’ reactions and plan the new steps with accuracy, clearing level after level. The ghosts never adapted.

By the age of twelve, the boy knew that he would become a “computer engineer”. Every occupational counselor (two in total) advised against this decision, not because it was bad, but because the counselors didn’t know anything about the profession. But the boy sticked to his decision and began his studies in computer science immediately after school was over. This was in 1997, when the internet still made sounds and you could ruin an hour-long download just by picking up the phone.

The boy, now a young man far from home, studied basic computer science for six month until the semester break arrived. Most other students returned home, but he stayed and teamed up with other students still on campus. They planned to program a computer game. A pac-man game, but with multiplayer abilities. One team would be “the players” or “pac-men”, the other team would be “the ghosts”. If somehow there wouldn’t be a dozen human players in front of the keyboard, the computer would control the remaining avatars. Game controls worked with split keyboard and – planned for later versions – over the network.

The only way the students knew how to organize the project was to transform one room into a computer-ridden workshop and hack away. Every horizontal platform in the room became a desk. The project should happen in a span of 24 hours. Today, this would be called a “game jam“. After 24 hours, all we had was a map. No game, no players, nothing exciting – just the future game’s map. But we agreed to continue working until the game is finished.

It took the three students a whole week. A week without much sleep, slippy food and lots of source code. Because we didn’t know about version control yet (nobody told us and we didn’t set up a local network, anyway), we had to structure the code in way that would allow us to work on different parts without collisions and transfer them from computer to computer using floppy disks. We had to maintain a list of files that were modified and did so on a central whiteboard that the young man had bought at the beginning of his studies. This whiteboard became the planning area where we would keep track of our modifications, tasks and concepts, including the stereotypical post-it notes. In hindsight, you could call it a chaotic story board. Without the whiteboard, we probably would have failed.

But after the week, the game was finished. We had developed a multiplayer pac-man in Java, complete with graphics, sounds and multi-threading. It was playable! We named it “Hubert 2D”, a reference to both “Duke Nukem 3D”, a very 90s game, and to one of our most famous fellow students. The game was blazingly fast – so fast, in fact, that you often lost track of your avatar. The unofficial motto of the game turned out to be “where am i?”. It was crammed with features. Just a Pac-Man where you could gobble up little pills and evade the ghosts was not enough for us. First, there was Hubert, the boss ghost. He appeared randomly and could not be player-controlled. He had a rocket launcher. If you defeated Hubert, you could grab the rocket launcher and, well, launch rockets. How can you defeat a rocket-launching ghost in Pac-Man? With your chainsaw, evidently. Players could pick up chainsaws to defend themselves against the ghosts. Ghosts could pick up energy shields to defend themselves against the chainsaws. Players could place mines to blow up ghosts that didn’t pay attention. Ghosts could place bombs to create new passageways to evade the mines or blow up the players. Sheep wandered around cluelessly, being blown up by mines, bombs, chainsaws or rockets and generally acting like a mobile roadblock. Teleporters added to the confusion by instantly teleporting you to either another teleporter or a random place on the map (leading to the infamous “where am i?”). But above all, you could poison and heal other avatars with various potions. Taking everything into account, this wasn’t Pac-Man anymore. This was team deathmatch that lasted until all the pills on the map were gobbled up accidentally.

Two funny moments during development and testing (aka playing) will always stay in my memory:

• You could poison an avatar, but also heal it with medicine. Being healed was indicated by an “hallelujah” sound effect. But, because every new avatar on the map would be created in the “healed” state, we had a serious “hallelujah” epidemic going on. It took us way longer than it should have to connect the dots and eliminate the sound effect during creation.
• Every avatar on the map moved with the same speed. Some avatars like bombs or mines decided not to move at all, others like sheep and Hubert only moved sometimes, but rockets flew twice as fast. So it was not possible to outrun a rocket. Because of this imbalance in power, we deemed the Hubert boss to be invincible in close combat. You could not walk up to him without facing a rocket that reached you at least a tile before you could employ your chainsaw. We were proven wrong, when one player used an energy shield in combination with a chainsaw and a hallway corner to sneak up on Hubert, neutralize the first rocket with the energy shield and defeat Hubert with the chainsaw before the second rocket could be fired. Because we thought that Hubert would be invincible, this move didn’t gain any in-game points. But the moment turned legendary immediately.

This week of intensive teamwork, combined with the result of an actual game, provided us with the trust and groundworks for future collaboration. So it was no wonder that, just a few semesters later, we came up with the idea of selling this collaboration ability in the form of a software development company. We were more knowledgeable, better equipped and had trained working together multiple times. What better times than now?

So we founded our company, the Softwareschneiderei (“software tailoring”) in late 2000, twenty years ago. Because we really meant it to be earnest, we invested the money to create a limited liability company and had to learn all the topics and obligations that follow such a creation in a very short time. We were still studying at university, but working for our own company, in a rented office, in every free minute. Our primary goal was to finish our studies with a degree. Our secondary goal was to let the company survive long enough to make it the primary goal after graduation. The plan worked out and here we are, twenty years later.

The statistics says that only one out of ten companies survives their first five years. Even after that, keeping a company afloat is not sunshine sailing. Somehow, we made it. Despite all our mistakes and misconceptions (and there were many, most on a more serious level than deeming Hubert to be invincible), we developed our company in a way that provides benefit for our customers and profit for our employees.

And in a corner of my desk drawer, there is still a 3,5″ floppy disk labelled “Hubert 2D”. Because that’s the source code that got this company started, 23 years ago.