An editorial comment:

For R7RS large we have retired the phrase ‘it is an error’ and replaced it with ‘undefined behaviour’, because it is less misleading to modern programmers about what was actually meant by that phrase in the reports. (We are also replacing many instances of ‘undefined behaviour’ with stricter requirements.)
<https://codeberg.org/scheme/r7rs/issues/184>

The phrase ‘it is an error’ is still used throughout SRFI 257. While I don’t think SRFI authors should be required (yet) to adopt the new convention, it would be nice to see it adopted more widely, and help alleviate confusion about what implementations might actually do in these situations.

Daphne

On 25 Nov 2025, at 00:49, Arthur A. Gleckler <xxxxxx@speechcode.com> wrote:

> Sergei Egorov, author of SRFI 257: Simple extendable pattern matcher with backtracking, has asked me to announce last call for this SRFI. He believes that it is ready for finalization, but would like to give reviewers one last chance to submit corrections and feedback before we finalize it.
> In particular, I appeal to anyone reading this to try the sample implementation, run the tests, and send feedback about your results.
> If you're interested in this SRFI, please give your feedback via the SRFI 257 mailing list before 2025-12-15. After that, assuming that no major revisions are required, we will declare it final. It is important that we get your feedback before 2025-12-15. If that deadline is too soon for you, but you would like to contribute, please let me know so that I can extend the last-call period.
> Regards,
> SRFI Editor