Yes, that works generally. An implementation is not permitted to implement (values) by returning NIL because that would be detectable by multiple-value-list for example.
The "primary value" is used in cases where a form has to yield a value, such as in a let binding or as an argument to a function. In those cases, nil is used if there are zero values. (when nil (values)) will always return one value, nil, because (values) is never evaluated there. Likewise, (when t (values)) will always return zero values. __Martin >>>>> On Fri, 9 Jun 2023 08:35:29 -0500, Robert P Goldman said: > > Does that generally work, or is an implementation permitted to implement > (values) by returning NIL? > > In the description of “primary value” in the hyper spec, I see the following: > > > primary value n. (of values resulting from the evaluation of a form) the > first value, if any, or else nil if there are no values. ``The primary value > returned by truncate is an integer quotient, truncated toward zero.'' > > Does that license `(when nil (values))` to return NIL? > > -- > Robert P. Goldman > > On June 9, 2023 at 08:23:46, Martin Simmons > (mar...@lispworks.com(mailto:mar...@lispworks.com)) wrote: > > > Another possible fix is to always return zero values, e.g. > > > > #.(progn > > (when (uiop:getenv "HOMEBREW_PREFIX") > > (pushnew :homebrew *features*)) > > (values)) > > > > __Martin > > > > > > > > > > > On Thu, 08 Jun 2023 16:32:36 -0500, Robert Goldman said: > > > > > > This one was my fault. I did the PR with this patch, because cl-libuv > > > wouldn't build on my Mac. Since there's no testing, apparently, it > > > slipped through. > > > > > > I don't know how to fix this, because I have never used CFFI-grovel, so > > > no idea how to put Madhu's advice into practice. > > > > > > As an aside, doesn't this kind of break Faré's design principle that the > > > person who has the information is the one who should be configuring the > > > software? It seems like we are expecting the programmer to guess ahead of > > > time what are all of the possible locations for the foreign library and > > > includes. Wouldn't it make more sense for this to be configurable? > > > > > > Of course, this is partly my fault, since ASDF does not support > > > configuring operations, except with gross dynamic variables. > > > > > > On 8 Jun 2023, at 15:32, Attila Lendvai wrote: > > > > > > > FTR, Madhu's analysis has been forwarded to the author: > > > > > > > > https://github.com/orthecreedence/cl-libuv/issues/23 > > > > > > > > -- > > > > • attila lendvai > > > > • PGP: 963F 5D5F 45C7 DFCD 0A39 > > > > -- > > > > “Nobody in the world, nobody in history, has ever gotten their freedom > > > > by appealing to the moral sense of the people who were oppressing > > > > them.” > > > > — Assata Shakur (1947–) > > > > > > >
