I've found that (rx (|)) doesn't work (I wanted to use it to easily
kill off certain "branches" of a regexp while maintaining submatches).
I traced it as far as compile-regexp in re-high.scm, which was calling
regexp->posix-string (which returns [#f #f #f #f]), then calling
(new-cre #f #f).
Here's a log of the error:
Welcome to scsh 0.6.4 (Olin Shivers)
Type ,? for help.
> (rx (|))
1> (regexp-search re-empty "test")
BTW, minor corrections for the manual:
- make-re-seq, re-seq, make-re-choice, re-choice aren't [any longer?]
- regexp->posix-string returns 4 values, not 1.