APL Seeds ’22: Tuesday 29 March

On Tuesday 29 March we hosted APL Seeds ’22, the second annual online event for new and prospective users of APL (although everyone was welcome). Once again we were delighted to see that the majority of registrants had little to no APL experience; it feels like we get the chance to offer that same sense of discovery we felt when first learning about the language.

APL Seeds ’22 began with an introduction from Dyalog Ltd’s managing director, Gitte Christensen, in which she described her experiences of seeing APL enable people who had real problems to solve and showed some of what Dyalog provides in terms of the tools and interfaces that people might expect from a modern software development stack. Gitte explained the new Basic Licence, which is another step forward in Dyalog Ltd’s aim to bring APL to a wider audience. The Basic Licence allows non-commercial distribution of Dyalog along with APL-based solutions under the terms of the Royalty-Based Run-Time Licence, which will apply as the default run-time licence (see Prices and Licences for more information on Basic Licences). She also described some customer use cases, some of which might surprise newcomers to this language. Rich Park finished the introduction by pointing out where you can find more APL content, especially if you’re just getting started. For example, our tips for beginners includes things that might not be obvious when you first start the interpreter or read introductory books. The video description for the recording of this presentation contains many useful links!

APL is an executable notation and tool of thought which enables people with good ideas to bring them to life with computers

Gitte opens the event with her thoughts on “What is APL?”, including the short expression 1 2 3 + 4 5 6 that started the journey which eventually brought her to Dyalog.

Rich then presented a basic introduction to APL, showing the benefits of a symbolic notation for programming as well as demonstrating how to put together simple building blocks to build a function. After introducing the basic syntax, right-to-left precedence, and the generality of APL operators, along with a handful of symbols including the famous outer product (⍺∘.F⍵) and array indexing (⍺[⍵]), he walked through constructing a function that visualised the probability distribution for sums of rolling two N-sided dice.

A screenshot of an APL function to do some simple statistical computation and display the output using characters in the APL REPL

The Dist function uses just a handful of APL constructs to create a visualisation of a simple statistical distribution.

Stefan Kruger, author of the online book Learning APL, took us on an exploration of bioinformatics problems – a popular topic for the annual APL Problem Solving Competition. He described what a “k-mer” is (a chunk of DNA of a particular length), and compared different techniques for cutting up a text vector to isolate them from a DNA string, including a windowed-reduction (⍺F/⍵) and its generalised cousin, the stencil operator ((⍺⍺⌺⍵⍵)⍵), and our old friends the outer product and array indexing. Finally, Stefan looked at three approaches to doing some simple statistics in the Rosalind challenge “Computing GC Content“. To our delight, a new user who was in attendance commented that they learned new expressions and idioms that they had not seen before.

Stefan compares 3 functions to split a string into lengh-4 substrings

Stefan compares 3 functions to split a string into lengh-4 substrings

Andrew Sengul presented a more involved example, April. The April APL Compiler is a new entry in the APL field, compiling a subset of APL into the Common Lisp language and allowing APL functions to easily be used within Common Lisp programs. Andrew gave a concise history comparing Lisp and APL. He then gave a small introduction to using Lisp to write a “macro” (code that generates other code) before giving a glimpse into the implementation, architecture and design of APL in Common Lisp, as well as code that combines APL and Lisp to create visualisations. He showed a visualisation that used APL to both run Conway’s Game of Life and apply convolution kernels to show the state of cells over time. We loved seeing how he has been using April in the visual art installation Bloxl (a collection of computer-controlled light-up blocks used at events for a stunning visual effect). Andrew concluded his presentation with a demonstration of April code implementing a “falling block game”, and a video of that game in action.

Andrew gives a comparative overview of the histories of the APL and Lisp programming languages

Andrew gives a comparative overview of the histories of the APL and Lisp programming languages

Finally, there was a live recording of an episode of Array Cast, a semi-weekly podcast about array languages. From the regular panel of presenters were self-proclaimed J enthusiast Bob Therriault, Kx Librarian Stephen Taylor, Dyalog tools developer and life-long APL programmer Adám Brudzewsky, and professional C++ developer and programming language fanboy Conor Hoekstra. They were joined by a very special panel of guests: speakers from the event Gitte Christensen, Rich Park, Stefan Kruger, and Andrew Sengul, and well-known APLers Aaron Hsu and Rodrigo Girão Serrão.

The discussion began with the common beginners’ questions of keyboards, typing APL and whether you really need stickers, keycaps or a whole dedicated APL keyboard to use APL. On the topic of actually learning APL, there were mentions of even more books and other resources, including YouTube channels run by some of the podcast panellists and guests. All relevant links are included in the show notes for the episode, and you can listen to the episode on arraycast.com.

Taking a more technical turn, there was discussion of the balance between code clarity and performance. Should code be clear unless absolutely performance critical? Or is it possible to have both, where the clearer encodings and approaches are also the fastest? The episoded was capped off nicely, in response to a question from the audience, with Gitte offering her perspective on how APL can help a data analyst or engineer.

In the informal meet-up after the talks, Andrew configured a simple interface to the aforementioned “falling block puzzle game”, in which participants could control the game and see their moves played out on a Bloxl wall streamed in real (if a bit delayed) time. The players tried their best but were ultimately thwarted by the interface of clicking buttons using Zoom shared controls!

To those who attended, we hope you found the event enjoyable. Relevant materials have been uploaded to the APL Seeds ’22 webpage, including links to recordings of the presentations on dyalog.tv.

APL Seeds ’21: Wednesday 31 March

Last Wednesday we hosted APL Seeds ’21, an event for those just starting their APL journey. Although we knew we had a good programme with some exceptional presenters in place, we very quickly had to increase our Zoom webinar limit to accommodate the 287 people who registered to attend! We were surprised and excited by the demographic, spanning 32 countries and with the vast majority having only basic or no APL experience.






The meeting started with a brief introduction from Dyalog’s Managing Director, Gitte Christensen, who shared her initial “Eureka” APL moment and gave some examples of situations in which APL is used today. Richard Park then took us on a whirlwind tour of APL’s past (including the very cool 1975 APL demonstration!) before demystifying the “beautiful squiggles” that define APL and introducing the modern resources that are available for learning APL (for a summary of these see the suggestions for learning resources available on our website).

The main presentations began with Rodrigo Girão Serrão giving a basic introduction to APL functions and syntax. Using the example of manually justifying text, he showed just how natural it is to process data in arrays by combining a few functions and operators. His initial exploration using a small snippet of text worked instantaneously and without issue on a whole book. After seeing this, hopefully you’ll feel an urge to learn some more – either because you got hooked (like Rodrigo did!) or simply because you want to learn how to think in an array-oriented way, which is very relevant in many situations today, such as when working with GPUs.

Martin Janiczek used a real-life example from the market insights and consumer trends company that he works for (GWI). Despite being a self-described “APL baby”, having learned APL for only around a month, he was able to get to grips with the tree structures that he wanted to use, and talked about how learning APL led him to change his overall approach to the problem. He achieved a highly-performant working prototype in two weeks and with only 172 lines of code, despite starting from the position of a complete APL beginner. Although ultimately his APL model was not taken into production, it inspired a complete rethink and new approach in the eventual product.

Conor Hoekstra (NVIDIA) describes himself as “not an APLer but a big fan”, and his enthusiasm is obvious and contagious! His explorations in APL are YouTube famous, and here again he deftly shows how APL can be used as a tool of thought to explore problems from many different angles with relative ease. He went through multiple different solutions to writing an All Equals function (is every element in a list the same as every other element?), playing with different primitives and comparing the performance of the solutions.

The final presentation came from Tomas Gustafsson, creator of the stunning Stormwind boating simulator. Tomas introduced the technology behind the 3D engine that he uses for his simulator, explaining the code that makes it all happen, before walking us through creating some simple 3-D shapes (a rotating triangle and an icosahedron) and the pitfalls that this entails. From the comments we know he seemed to inspire several members of the audience to want to know more… so for those of you that do, his code examples will soon be available from the APL Seeds web page.

We hope everyone found the event useful and enjoyable (the feedback seems to indicate that you did – thank you!). Relevant materials have started to be uploaded to the APL Seeds ’21 webpage – this page also includes links to recordings of the presentations, which are all on dyalog.tv: