Is it worth it having a separate use-case layer? When I occasionally post something about Ports and Adapters (also known as hexagonal architecture), a few reactions seem to indicate that I'm 'doing it wrong'. I apologize for the use of weasel words, but I don't intend to put part … | Continue reading
Giving advance warning before breaking client code. I was recently listening to Jimmy Bogard on .NET Rocks! talking about 14 versions of Automapper. It made me reminisce on how I dealt with versioning of AutFixture, in the approximately ten years I helmed that project. Jimmy has … | Continue reading
No, it's not a typo. A few months ago, I was listening to a semi-serious programme from the Danish public service radio. This is a weekly programme about language that I always listen to as a podcast. The host is the backbone of the show, but in addition to new guests each week, … | Continue reading
IObservable is (also) a monad. This article is an instalment in an article series about monads. While the previous articles showed, in great detail, how to turn various classes into monads, this article mostly serves as a place-holder. The purpose is only to point out that you do … | Continue reading
A metaphor. While I'm still struggling with the notion that dynamically typed languages may have compelling advantages, I keep coming back to the benefits of statically typed languages. One such benefit is how it enables the communication of contracts, as I recently discussed in … | Continue reading
Programming isn't like factory work. I was recently stuck on a programming problem. Specifically, part two of an Advent of Code puzzle, if you must know. As is my routine, I went for a run, which always helps to get unstuck. During the few hours away from the keyboard, I'd had a … | Continue reading
Seven lines of Python code. Can you tell what this is? I showed this to both my wife and my son, and they immediately recognized it for what it is. On the other hand, they're also both culturally primed for it. After all, it's a map of Denmark, although I've transformed each of t … | Continue reading
A C# example implementation of Ghosts of Departed Proofs. This article continues where Modelling data relationships with F# types left off. It ports the F# example code to C#. If you don't read F# source code, you may instead want to read Implementing rod-cutting to get a sense o … | Continue reading
Here, have a sandwich. For years I've been thinking about the Dependency Inversion Principle (DIP) and Inversion of Control (IoC) as two different things. While there's some overlap, they're not the same. To make matters more confusing, most people seem to consider IoC and Depend … | Continue reading
An F# example implementation of Ghosts of Departed Proofs. In a previous article, Encapsulating rod-cutting, I used a code example to discuss how to communicate an API's contract to client developers; that is, users of the API. In the article, I wrote "All this said, however, it' … | Continue reading
A pattern variation. After writing the articles Collecting and handling result values and Short-circuiting an asynchronous traversal, I realized that it might be valuable to describe a more disciplined variation of the Impureim Sandwich pattern. The book Design Patterns describes … | Continue reading
Focusing on usage over implementation. This article is a part of a small article series about implementation and usage mindsets. The hypothesis is that programmers who approach a problem with an implementation mindset may gravitate toward dynamically typed languages, whereas deve … | Continue reading
One major attraction of Python. A recent realization. Ever since I became aware of the distinction between statically and dynamically typed languages, I've struggled to understand the attraction of dynamically typed languages. As regular readers may have noticed, this is a bias t … | Continue reading
From pseudocode to implementation in three languages. This article picks up where Implementation and usage mindsets left off, examining how easy it is to implement an algorithm in three different programming languages. As an example, I'll use the bottom-up rod-cutting algorithm f … | Continue reading
An Impureim Sandwich example in C#. When learning functional programming (FP) people often struggle with how to organize code. How do you discern and maintain purity? How do you do Dependency Injection in FP? What does a functional architecture look like? A common FP design patte … | Continue reading
A one-dimensional take on the enduring static-versus-dynamic debate. It recently occurred to me that one possible explanation for the standing, and probably never-ending, debate about static versus dynamic types may be that each camp have disjoint perspectives on the kinds of pro … | Continue reading
Another C# example. This article is a continuation of an earlier post about refactoring a piece of imperative code to a functional architecture. It all started with a Stack Overflow question, but read the previous article, and you'll be up to speed. Imperative outset # To begin, … | Continue reading
You can stack some monads in such a way that the composition is also a monad. This article is part of a series of articles about functor relationships. In a previous article you learned that nested functors form a functor. You may have wondered if monads compose in the same way. … | Continue reading
The answer is traverse. It's always traverse. I recently came across a Stack Overflow question about collecting and handling sum types (AKA discriminated unions or, in this case, result types). While the question was tagged functional-programming, the overall structure of the cod … | Continue reading
How to convert a list of tasks into an asynchronous list, and similar problems. This article is part of a series of articles about functor relationships. In a previous article you learned about natural transformations, and then how functors compose. You can skip several of them i … | Continue reading
Are Haskell IDE plugins now good enough that you don't need explicit type annotations? More than three years ago, I published a small article series to document that I'd changed my mind on various small practices. Belatedly, here comes a fourth article, which, frankly, is a cousi … | Continue reading
A functor nested within another functor forms a functor. With examples in C# and another language. This article is part of a series of articles about functor relationships. In this one you'll learn about a universal composition of functors. In short, if you have one functor neste … | Continue reading
A translation of the kata, and my first attempt at it. In early 2013 Richard Dalton published an article about legacy code katas. The idea is to present a piece of 'legacy code' that you have to somehow refactor or improve. Of course, in order to make the exercise manageable, it' … | Continue reading
A choice of two or more functors gives rise to a functor. An article for object-oriented programmers. This article is part of a series of articles about functor relationships. In this one you'll learn about a universal composition of functors. In short, if you have a sum type of … | Continue reading
Package a constant value, but make it look like a functor. An article for object-oriented programmers. This article is an instalment in an article series about functors. In previous articles, you've learned about useful functors such as Maybe and Either. You've also seen at least … | Continue reading
A puzzle kata, and a possible solution. When I was a boy I had a nine-piece puzzle that I'd been gifted by the Swizz branch of my family. It's called Das verflixte Hunde-Spiel, which means something like the confounded dog game in English. And while a puzzle with nine pieces does … | Continue reading
Another functional model of a file system, with code examples in C#. This article is part of a series about Zippers. In this one, I port the FSZipper data structure from the Learn You a Haskell for Great Good! article Zippers. A word of warning: I'm assuming that you're familiar … | Continue reading
A tuple or class of functors is also a functor. An article for object-oriented developers. This article is part of a series of articles about functor relationships. In this one you'll learn about a universal composition of functors. In short, if you have a product type of functor … | Continue reading
A port of another Haskell example, still just because. This article is part of a series about Zippers. In this one, I port the Zipper data structure from the Learn You a Haskell for Great Good! article also called Zippers. A word of warning: I'm assuming that you're familiar with … | Continue reading
Don't inject third-party dependencies. Use Decorators. I recently came across a Stack Overflow question that reminded me of a topic I've been meaning to write about for a long time: Cross-cutting concerns. When it comes to the usual suspects, logging, fault tolerance, caching, th … | Continue reading
A port of a Haskell example, just because. This article is part of a series about Zippers. In this one, I port the ListZipper data structure from the Learn You a Haskell for Great Good! article also called Zippers. A word of warning: I'm assuming that you're familiar with the con … | Continue reading
Some functional programming examples ported to C#, just because. Many algorithms rely on data structures that enable the implementation to move in more than one way. A simple example is a doubly-linked list, where an algorithm can move both forward and backward from a given eleme … | Continue reading
A data architecture example in C# and ASP.NET. This is part of a small article series on data architectures. In this, the third instalment, you'll see an alternative way of modelling data in a server-based application. One that doesn't rely on statically typed classes to model da … | Continue reading
A data architecture example in C# and ASP.NET. This is part of a small article series on data architectures. In this, the second instalment, you'll see a common attempt at addressing the mapping issue that I mentioned in the previous article. As the introductory article explains, … | Continue reading
A data architecture example in C# and ASP.NET. This is part of a small article series on data architectures. In the first instalment, you'll see the outline of a Ports and Adapters implementation. As the introductory article explains, the example code shows how to create a new re … | Continue reading
A comparison, for educational purposes. Use the right tool for the job. How often have you encountered that phrase when discussing software architecture? There's nothing wrong with the sentiment per se, but it's almost devoid of meaning. It doesn't pass the 'not test'. Try to neg … | Continue reading
Software development in a globalized, hostile world. Imagine that you're perusing the thriller section in an airport book store and come across a book with the following back cover blurb: Programmers are dying. Holly-Ann Kerr works as a data scientist for an NGO that fights workp … | Continue reading
Async and await are notorious for being contagious. Must all interfaces be Task-based, just in case? I recently came across this question on Mastodon: "To async or not to async? "How would you define a library interface for a service that probably will be implemented with an in m … | Continue reading
With examples in C# and F#. This article is part of a series about encapsulation and immutability. After two attempts at an object-oriented, mutable implementation, I now turn toward immutability. As already suggested in the introductory article, immutability makes it easier to m … | Continue reading
An encapsulated, albeit overly complicated, implementation. This is the second in a series of articles about encapsulation and immutability. In the next article, you'll see how immutability makes encapsulation easier, but in order to appreciate that, you should see the alternativ … | Continue reading
An instructive dead end. This article is part of a short series on encapsulation and immutability. As the introductory article claims, object mutation makes it difficult to maintain invariants. In order to demonstrate the problem, I deliberately set out to do it wrong, and report … | Continue reading
A worked example. I've noticed that many software organizations struggle with encapsulation with 'bigger' problems. It may be understandable and easily applicable to define a NaturalNumber type or ensure that a minimum value is less than a maximum value, and so on. How do you, ho … | Continue reading
Beating another dead horse. Although I live in Copenhagen and mostly walk or ride my bicycle in order to get around town, I do own an old car for getting around the rest of the country. In Denmark, cars go through mandatory official inspection every other year, and I've been thro … | Continue reading
An illustrative example. More than a decade ago, I worked on a small project. It was a small single-page application (SPA) with a REST API backend, deployed to Azure. As far as I recall, the REST API used blob storage, so all in all it wasn't a complex system. We were two develop … | Continue reading
How to stay current with technology progress. A long time ago, I landed my dream job. My new employer was a consulting company, and my role was to be the resident Azure expert. Cloud computing was still in its infancy, and there was a good chance that I might be able to establish … | Continue reading
Some thoughts on developer experience. Years ago, I was introduced to a concept called developer ergonomics. Despite the name, it's not about good chairs, standing desks, or multiple monitors. Rather, the concept was related to how easy it'd be for a developer to achieve a certai … | Continue reading
An API design heuristic. For a while now, I've been wondering whether, in the language of Postel's law, one should favour being liberal in what one accepts over being conservative in what one sends. Yes, according to the design principle, a protocol or API should do both, but som … | Continue reading
A reading of the fourth Don Box tenet, with some commentary. This article is part of a series titled The four tenets of SOA revisited. In each of these articles, I'll pull one of Don Box's four tenets of service-oriented architecture (SOA) out of the original MSDN Magazine articl … | Continue reading