The program for BOB 2026, Active Group‘s in-house conference, is set: On Friday, March 13, 2026, BOB - appropriately the thirteenth edition - will take place — as last year at the Scandic Hotel Potsdamer Platz.

We are proud of the program, although we had to reject many other great submissions to create it.

The opening keynote at BOB will be delivered by Stefan Kaufmann (stk) — it‘s about Digital Sovereignty.

As usual, there are four tracks — two tracks with a total of 16 talks, two tracks with a total of 8 tutorials.

Registration is open — the early-bird discount runs until January 16, 2026.

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While working on the paper „Evolution of Functional UI Paradigms“, published at the FUNARCH workshop of ICFP 2025, I had a thought about pure functions that I would like to briefly explain here. As an argument in favor of pure functions, functional programmers often cite better testability: pure functions require no complicated test setup or mocks, are deterministic, parallelizable, etc. In tendency, this is certainly correct. Pure functions are often better suited for testing than their impure counterparts. However, this connection is not a neccessary implication in either direction: There are pure functions that are hard to test, and there are impure functions that are easy to test. Thus purity itself cannot be the substance that ensures a piece of program is properly testable. But then what is this substance?

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On March 13, 2026, BOB, Active Group‘s conference about the best in software development, will take place — once again in Berlin and once again at the Scandic Berlin Potsdamer Platz.

The Call for Contributions is open. Send us your proposal for a talk or tutorial (by November 17, 2025) — the program committee is looking forward to it!

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This is an English translation of the German version of this post.

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This post is part of the series on functional software architecture in Kotlin. The first one covered functional validation, and this part is about monads. In Kotlin, these are particularly useful when describing domain workflows that should be separated from the technical logic for executing these workflows - specifically using small domain-specific languages (DSLs).

This episode is about how monads actually work. Kotlin has - like many functional languages - special syntax for this, even though you won‘t find it under the „M-word“ in the documentation. It‘s hidden behind the suspend keyword.

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