APL Seeds '22

Dyalog Ltd's CEO opens the user meeting and offers some perspective from her experience, before Rich talks about the APL community and the resources available to those just getting started.

APL has a reputation for being difficult to read – but of course that's only true if you don't know how to read it! Rich offers a basic introduction to APL (like Hangul, you can probably learn enough to "read" in about 20 minutes), while acknowledging that it is the surrounding viewpoint, ways of thinking, approaches to problem solving, and ability to readily experiment with ideas, that make APL both more challenging and more rewarding.

Stefan dips his toes into the world of Computational Genomics, discovering an area with real APL affinity. During his talk, he works through a couple of problems from Project Rosalind, perhaps providing a bit of a starting point for future APL Problem Solving Competition solutions in the process, as problems from Project Rosalind occasionally provide inspiration for this!

Links referred to during Stefan's presentation:

• https://xpqz.github.io/learnapl
• https://xpqz.github.io/cultivations
• https://xpqz.github.io/kbook
• https://problems.tryapl.org/psets/2017.html?goto=P6_k_mers
• https://rosalind.info/problems/gc/
• https://problems.tryapl.org/psets/2021.html?goto=P1_Are_You_a_Bacteria

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. The array models of Common Lisp and APL are similar, making it easy to pass data between Common Lisp and APL, and functions and operators written in Common Lisp can easily be added to April workspaces.

As with APL, developers using Lisp-family languages often interact with the language through a REPL, enabling an interactive style of development. This advantage extends to April, which benefits from Lisp's powerful set of development tools. Another unique benefit of April is the ability to easily extend and modify the language through a set of Lisp macros. You can build extensions to April, adding new functional characters in as little as 10 lines of code. Licensed under the permissive Apache 2.0 license, April has the potential to be customised for many use cases, and its close integration with Common Lisp allows it to be quickly integrated with many different external systems.

In this presentation, Andrew recounts the trials of developing and refining the April compiler. He also demonstrates Bloxl, a hardware startup powered by April that's creating lighted blocks that enable you to build walls, floors and other structures that also serve as light sources and visual displays. See APL used in ways you've never experienced before!

Useful links:

• April repository
• April paper (primarily written for a Lisp audience)
• April presentation at LispNYC

Conor Hoekstra is the host of The Array Cast, a panel-based podcast on array languages. Since launching a few months ago, Conor and his panellists have produced a series of extremely interesting podcasts, with special guests from many walks of Array Life. As the final session of APL Seeds '22, The Array Cast will be broadcast live.