If you check the HyperSpec entry for “trace”, you’ll see that it accepts implementation-specific additional arguments. I’m pretty sure I’ve seen other examples, but I cannot remember what they were just now.
> On 24 Jan 2023, at 10:47, Didier Verna <did...@didierverna.net> wrote: > > > Hello, > > Section 1.6 Language Extensions of the standard says this: > > A language extension is any documented implementation-defined behavior > of a defined name in this standard that varies from the behavior > described in this standard [...] > > > It is unclear to me if the term "behavior" could encompass additional > keyword arguments passed to a function or macro. I'm assuming here that > the rest of this section is honored (the additional arguments wouldn't > alter the confirming code, and their presence is not explicitly > prohibited). > > WDYT? > > -- > Resistance is futile. You will be jazzimilated. > > Lisp, Jazz, Aïkido: http://www.didierverna.info >