BQN is in a very early stage of development, and there is currently no complete implementation of the language. However, it's a relatively simple language to implement, and a few implementations come close.
BQN2NGN is a prototype implementation in Javascript build to experiment with the langauge, which is now abandoned. Because you can use it online, this is probably the quickest way to get started with BQN. It has good primitive support, with the main issues being that it uses a J-style insert instead of BQN-style vector reduction, that it has a different version of Group (⊔), and that it is missing Choose (◶). There are also some spelling differences, with Deduplicate (⍷) spelled with ∪ and Valences (⊘) spelled with ⍠. It is missing value blocks and function headers.
For automated testing I run BQN2NGN using the bqn executable, which is just a symlink to apl.js in the BQN2NGN repository. It requires Node to run.
dzaima/BQN is an implementation in Java created by modifying the existing dzaima/APL. It should be easy to run on desktop Linux and Android. It is still in development and has almost complete syntax support but incomplete primitive support.
This repository contains a dzaima/BQN script dzref that fills in the gaps in primitive support using BQN implementations of primitives which are not yet up to spec (reference implementations of all primitives starting from a small set of pre-existing functions are part of BQN's specification). These alternate implementations can be very slow.
You can run dzref from ordinary dzaima/BQN using the •EX command; see for example dcshim.bqn. For testing, it is run as a Unix script, in which case it depends on an executable dbqn that runs dzaima/BQN on a file argument. I use the following script, using the path to a clone of dzaima/BQN for the jar file.
#! /bin/bash java -jar /path/to/dzaima/BQN/BQN.jar -f "$@"
The left argument for •EX or the shell arguments can contain up to two arguments for the script. The first is a file to run, and the second is BQN code to be run after it.
This repository contains the beginnings of a self-hosted compiler for BQN, which is not yet complete enough to do any real programming with. There are currently several versions of the compiler: nc.bqn is run with BQN2NGN, while c.bqn is run with dzaima+reference. Both compilers have a backend targetting WebAssembly, and c.bqn additionally has a backend that targets dzaima/BQN's own bytecode, so that the compiler uses only BQN, but the runtime uses the Java implementations of BQN primitives from dzaima/BQN.
All versions have automated tests in the test directory, with the WebAssembly versions tested with Javascript using Node (test/t.js and test/dt.js for BQN2NGN and dzaima/BQN respectively) and the dzaima/BQN backend tested with BQN itself (test/bt).