I tried something new in the last few days: I built a #treesitter grammar for the FASTA file format!

https://jrhawley.ca/2026/04/19/tree-sitter-fasta

This was a fun learning experience and I'm quite happy with the result. I intentionally ignored "prior art" and built something for myself, so that I could see what kinds of questions and trade-offs I would need to grapple with.

If parsers, domain-specific languages, or bioinformatics are your interest, feel free to give this a try!