One more thing - how was (expt 0 z) extended to return 0 for complex z? The approaches I've tried would result in NaN, and indeed this seems to be what most implementations return.
-- Alex On Thu, Aug 16, 2012 at 9:50 AM, <w...@ccs.neu.edu> wrote: > Alex Shinn wrote: > >> What I'm more interested in is the unusual behavior >> that the result _either_ raises an exception _or_ returns >> an unspecified number. I believe this is the only place >> in any of the reports where the semantics is the disjunction >> of signalling an error and an unspecified value. What's >> the story behind this? > > I don't remember, but here's what I suspect. > > In the R5RS and earlier, the phrase "is an error" was used to > mean implementations were allowed to signal an error or to > return an arbitrary value, at their discretion. In the R6RS, > the "is an error" phrases were removed. Most of those phrases > turned into "an exception is raised", which represented a change > from the R5RS semantics, but not here. In this particular case, > the new language appears to be an attempt to preserve some of > the meaning of the R5RS "is an error" semantics. > > So I believe the language here is unusual because attempting > to preserve R5RS "is an error" semantics was unusual. > > Will _______________________________________________ r6rs-discuss mailing list r6rs-discuss@lists.r6rs.org http://lists.r6rs.org/cgi-bin/mailman/listinfo/r6rs-discuss
