Welcome Aarush Bhat

In pursuit of his dream to contribute to the development of a programming language professionally, Aarush started cold emailing companies that worked on them (there aren’t a lot, but a lot). One of the companies he contacted was Dyalog Ltd. Aarush initially joined us in January 2023 as a contractor, focusing on testing the primitives of the language with a new test suite, and in August he officially became a full-time member of the team.

Aarush’s interest in computers led him to a Bachelor of Technology Degree in Computer Science and Engineering from Vellore Institute of Technology, Vellore, India. Before joining Dyalog Ltd, Aarush explored various facets of web technologies and made significant contributions to projects like Haskell and Bitcoin. When not working professionally, he enjoys contributing to Open Source Software.

Expanding on his love for FOSS, he was selected for sponsored open-source programs like Google Summer of Code and Summer of Bitcoin while still pursuing his academic degree.

Beyond coding, Aarush finds joy in exploring Linux, programming languages, Bitcoin, and dreaming about new mechanical keyboards (he got one)! He also has a penchant for music, photography, F1 racing, and, perhaps most notably, travelling. The flexibility of remote work has allowed Aarush to explore new places and cultures. Due to his love for photography and spending money, he has recently also bought a 360 camera that he still cannot figure out how to turn into a useful webcam. πŸ™

Aarush is known on the internet as sloorush or, as his friends call him, rush (pronounced like bush).

Welcome Stefan Kruger

Stefan Kruger recently joined Dyalog Ltd from IBM, where he worked on distributed databases for many years.

Stefan spent a long time at university doing research in signal processing; after that he worked in several start-ups that were closely tied to the academic world. Then, taking a step away from technology for a while, Stefan pursued his interests in climbing and skiing, chasing winter around the globe until the money ran out.

Once safely back in gainful employment, Stefan set himself a goal of learning a new programming language each year, favouring those that are less mainstream…”the weirder, the better!”. This path has led him through such languages as Zig, Clojure, Elixir, Racket, Haskell, and many more. Once he discovered APL he was hooked. Recognising the need for more accessible resources while learning APL, Stefan wrote Learning APL, an introductory book for programmers familiar with other languages; he also edited together APL Cultivations, which covers most aspects of basic APL programming as well as some more in-depth lessons.

Stefan lives in Bristol with his wife Sarah, two cats, one dog, and n+1 bikes. He enjoys back country skiing in arctic Scandinavia or Canada during his winter holidays. In the summer, he stays active by road biking, especially climbing the classic cols in the Alps β€” strictly “type 2” fun.

We’re glad to have Stefan on board at Dyalog Ltd; his background and drive for continuous learning should be a positive contribution to our team, and we look forward to seeing his contributions to the APL community.

Employee Spotlight: Peter

This week marks the first anniversary of Peter joining Dyalog Ltd. He is one of the newest additions to Team Dyalog and we couldn’t be more excited for his future here. We were able to pry him away from the interpreter to catch up with him and see what his time has been like so far.

Peter joined Team Dyalog after studying at Aalborg University, where he received his Bachelor’s degree in computer science. APL made an impression on him when he heard about it in 2021; he found it fresh and pleasantly new. APL (and Dyalog APL) were different from other programming languages he had dealt with.

Most days Peter is deeply involved with Dyalog’s interpreter; he improves it by implementing cool new features and fixing any annoying bugs. Peter really enjoys the affable and cooperative culture here at Dyalog Ltd, “It is a very friendly crowd, and everyone is willing to help me with whatever issue comes up.” He also enjoys his role in the development team. He finds it challenging and fulfilling to work on issues that require him to look at and understand a part of code that he hasn’t seen before…it’s like solving a puzzle for him, and when things start to ‘click’ he gets really motivated because he knows, “that the system is becoming more and more robust with every bug fix.” Peter’s role requires a lot of critical thinking, “I think the most important skill is to be able to navigate and make sense of old code on your own.”

When he’s not improving the heart of Dyalog, you can find Peter spending his time outside! (I know, shocking for a programmer!) He enjoys scenic walks in the picturesque nature local to him in Denmark, which is a huge juxtaposition from staring at screens for a living.

Peter is a great addition to the team, and we wish him all the best on his one-year anniversary at Dyalog Ltd.

Welcome Jada Andrade

Jada moved to the United Kingdom in 2015 to pursue a degree in law with politics at the University of Manchester. On graduation she relocated to Reading in the south of England, where she took on various temporary positions in administration during the Covid-19 pandemic.

Jada first heard about APL when her partner, Rich Park, joined Dyalog Ltd in October 2018. Since then, she has attended various Dyalog Ltd events as a guest, including Dyalog ’19 and Dyalog ’22, and found the enthusiasm and passion of the APL community infectious, despite having little to no experience in computing. Attending these events left Jada with a very positive impression of Dyalog Ltd, particularly with the logistical planning and administrative organization evident from the smooth running of each event. She was also in the unique position of being able to interact with Dyalog Ltd employees prior to joining the company, fostering good relationships through casual communication.

Therefore, when the possibility of joining Team Dyalog as an administration assistant and office manager was brought up, she immediately jumped on the opportunity and officially joined the company towards the end of March 2023. She hopes to lessen the current workload of the administration team, and enjoys the varied nature of her role as she gets to explore legal, finance, customer relations and office management tasks.

Outside work, Jada enjoys improving her running skills, taking long walks in the bountiful nature of Berkshire, occasionally canoeing, discovering cool Japanese manga, and making delicious dishes in the kitchen.

11 April 2023 – A Day to Celebrate!

Today we reach two very significant milestones.

40 Years of Dyalog APL

On this day, we have cause for celebration: it is 40 years since the release of Dyalog version 1.0! Geoff Streeter would say that from his perspective we are already in the 42nd year, as he and John Scholes started work on the new interpreter in 1981. On the other hand, Pete Donnelly might argue that the interpreter wasn’t really ready for serious use until a few years after that date. The fact remains that the APL ’83 conference in Washington DC saw the first official release of the product, and is considered to be the “birth” of Dyalog APL.

Farewell Geoff Streeter

On the same day, we also congratulate Geoff Streeter, the last Dyalog developer who will have worked on the interpreter throughout its existence, on the first day of his retirement. We are happy to be able to report that, unlike John Scholes who designed and built version 1.0 together with Geoff but sadly passed away in 2019, Geoff is retiring in good health. We wish him many happy years in retirement in the company of his wife Sarah, children and grandchildren – although we are also hoping that he will pop by the Dyalog office from time to time to let us know how he thinks we are doing, and hopefully also join us at some future user meetings!


It is impossible to exaggerate the value of the dedication and continuity that Geoff and John provided to Dyalog over these four decades. In the early days, when company finances were shaky, they sometimes continued work on the interpreter without compensation. Today, we are still blessed with many team members who have worked for Dyalog for most, if not all, of their careers – although we are doing what we can to avoid the need for the extremes of dedication that were required in the early days.

Good Choices

Dyalog APL started its life as a unique combination of what was to become the leading nested array paradigm (APL2/NARS floating arrays) coupled with what John and Geoff (and the rest of the consulting team at Dyadic Systems Ltd) thought were the best “commercial” extensions selected from APL systems developed by STSC and I.P.Sharp Associates (component files and control structures from STSC, error trapping from IPSA, and many other features).

The early choices have stood the test of time, and paved the way for Dyalog to become extremely competitive when Windows 3.1 and John Daintree arrived at the same time – resulting in the extremely easy-to-use Win32 GUI support. In typical fashion, the team did not merely implement a tool for GUI programming, they adopted an approach that led to the very general notion of namespaces, which meant that the same architecture could be used to interface to COM/OLE and subsequently .NET and complete support for object-oriented programming in Dyalog.


Geoff was (and is) very much a UNIX man, and the first versions of Dyalog were built for the small UNIX machines that Dyadic Systems expected to take over from the mainframe. Unfortunately, UNIX was slow to gain acceptance and, around 1990 when UNIX was finally starting to take off, Microsoft Windows arrived and the centre of gravity of the commercial business shifted in that direction. Geoff was often heard muttering to himself about how the company was making poor technical choices, driven by what he referred to as “commercial” pressure. He kept his head down, and ensured the UNIX implementations were well supported and that all designs took the needs of these platforms into account.

Users of UNIX-based Dyalog can be grateful for Geoff’s unwavering enthusiasm. And Dyalog too: not only is the IBM AIX version of APL still a significant source of revenue, the ease with which we have been able to add support for Linux and macOS is very much down to our long UNIX history and the goal of maintaining cross-platform compatibility, throughout the history of the product.


As a further example of Geoff’s dedication: as a young man with a motorcycle and a keen sense of community, Geoff started riding at night, delivering blood from blood banks to hospitals where it was urgently needed. He started doing this in 1980, just after he started at Dyadic Systems, and, although he is retiring from Dyalog today, Geoff will continue as a volunteer for SERV S&L. Although he no longer rides his bike, he now acts as the controller for the new generation of riders. In October 2021, SERV S&L was presented with The Queen’s Award for Voluntary Service by the Lord Lieutenant of Surrey.

The Future

In the same way that Geoff has not been riding his bike at night, he has not been doing any new development on Dyalog for the last year. Instead, he has been preparing and holding internal presentations to a new generation of Dyalog developers, providing insight into the work that he has done over the last four decades. Ultimately an impossible task of course, but at least they now know where to start digging – and Geoff is still around to answer questions in an emergency if we offer him a cup of coffee and three plain chocolate digestives (his stated minimum requirement to come into the office!).

As Dyalog enters its fifth decade, all parts of Dyalog Ltd. (including the development team) are larger – and broader – than they have ever been. The good choices made by Geoff, John, Pete, and many others in the early years are holding up, and the company continues to grow.

Many thanks to Geoff from everyone at Dyalog Ltd. We will do our best to allow him to relax, enjoy his well-deserved retirement, and look forward to continued dividend payments from the Dyalog shares in his pension fund!


Welcome Peter Mikkelsen

Peter joined Dyalog Ltd in mid-July 2022, shortly after finishing his bachelor’s degree in Computer Science from Aalborg University in Denmark. He didn’t originally plan to look for a job so soon, but when he saw that Dyalog Ltd had an opening involving three of his favorite things (C programming, interpreters, and APL) it was too good an opportunity to let pass and he was offered the job after a couple of online calls and interviews. Peter and his girlfriend had planned to move to Esbjeg in the south-west of Denmark for a while, so he thought it was great that Dyalog Ltd made it possible to work from home. He joined just in time to be able to participate in Dyalog ’22, which meant that he met lots of customers, which he considered a great experience.

His interest in APL started while he was at university – at one point he thought to himself: “This language looks so strange and different that it might be worth learning.” After spending some time playing around with it and participating in the 2021 APL Problem Solving Competition, he started writing his own little APL interpreter, which he says must have been the point of no return for him. Even in the first few months at Dyalog Ltd, he has learned a great deal about the language and its quirks, and a lot about implementation techniques.

Peter hopes to be able to help develop the language in the years to come, and to make sure dfns get the love they deserve, as he thinks that functional programming is definitely the way to go!

Even though he is part of the “young generation” of APLers, writing long trains and doing code golfing in APL has yet to catch his interest.

When not working, Peter is likely to be found taking a long walk, or trying out something computer science related that has caught his interest. Often, the code he writes in his free time is for the Plan 9 operating system, which in his mind is so elegant and simple that it is almost a shame it has so few users.