Make note of related/alternative/useful projects

[klauer]

• https://github.com/nucleron/matiec (older ST compiler with parser) and updated version https://github.com/sm1820/matiec
• https://github.com/thiagoralves/OpenPLC_v3 (uses matiec, may have some customizations)
• https://github.com/PLC-lang/rusty (rust-based ST compiler)
• https://github.com/jubnzv/iec-checker (OCaml grammar + static analysis tool)
• https://github.com/Roald87/TcBlack Python black-like code formatter for TwinCAT code

Include comments from iec-checker author from #13:

Author of iec-checker here. I was alerted that you mentioned my project here, so I just want to add a few points about repositories listed above that I have worked with.

https://github.com/nucleron/matiec (older ST compiler with parser)

Matiec supports IEC61131-3 second edition, without classes, namespaces and other fancy features. If you decide to use it, I recommend applying the fixes from the company I worked for (see my recent commits). There were some segmentation faults in the parser that we found using fuzzing. After these fixes it seems pretty stable, and there haven't been any crashes in the few months of continuous fuzzing.
You may also be interested in the latest improvements in the parser in the upstream repository. They extended the parser with some constructs from CoDeSys and supported JSON dumps, which may be useful for you.

https://github.com/jubnzv/iec-checker (OCaml grammar + static analysis tool)

iec-checker has the ability to parse ST source code and dump AST and CFG to JSON format, so you can process it with your language of choice. This feature is used in test suite written in Python.
I'm not sure about the parser speed compared to other implementations, but I use menhir for the parser. This is a stable industrial grade LR(1) parser generator for OCaml and Coq.
The grammar completely covers IEC61131-3 3 ed. features used in the company I worked for. If something is missing there, you could create an issue in the repo.