-1. While the syntax has a basic beauty, it requires too much odd explanation. "*" and "**" are already binary operators. The '*' unary operator can confuse migrating programmers already. It makes puzzles too easy, e.g., yield **[2**3*i, for i in range(2*3**4)]
On Sat, Mar 15, 2008 at 6:55 PM, Phillip J. Eby <[EMAIL PROTECTED]> wrote: > At 06:33 PM 3/15/2008 -0500, Michael Urman wrote: > > > > I'm not sure how to solve this except by adopting a different syntax > > > > for the multiple-yield. Perhaps > > > > > > > > *yield x > > > > > > If there really were an inconsistency here, I would certainly not suggest > > > fixing it that way, yuuueghh. > > > >Agreed about *yield looking yucky. In a previous thread somewhere > >around http://mail.python.org/pipermail/python-dev/2006-January/059955.html > >a construct like "yield from x" was offered. It certainly helps > >clarify the difference between iteratively yielding the values from > >another iterator and yielding the values of an iterator as a tuple. > >While parsing rules do differentiate, I don't find the behavior > >obvious, and expect the differences between > > yield *x; yield *x(); yield *x,; yield (*x,); and yield *(x,) > >would become one of python's warts in a few years, if adopted. > > After following this thread for a bit, I think it's a wart > already. :) The potential for confusion with the other *assign > target idea is too high. > > I don't have a problem with "item for *item,val in blah", but "*item > for item in blah" makes my head hurt. Why not just say "i2 for i1 in > blah for i2 in i1"? Yes, it's a bit more verbose, but not frequent > enough to justify the *, and you can tell what's going on by > textually transposing to the nested for loops. Plus, it works for > any depth. What are you going to do if it's triple-nested? Use > **? What about ***? Where does it end? > > So I think "yield *" and "*item for item in..." are broken for the > same reason. In the function call use case, and in simple > assignment, it is treated as a literal quasi-textual > expansion. However, such an expansion in the yield case would yield > a tuple, and the literal expansion in the comprehension case would > make no sense. (If done by true textual substitution, it would have > to be a syntax error.) > > And I think that a quasi-textual substitution is the right mental > model for * expressions, as it's simple to explain and easy to reason > out what happens. > > > > _______________________________________________ > Python-3000 mailing list > Python-3000@python.org > http://mail.python.org/mailman/listinfo/python-3000 > Unsubscribe: > http://mail.python.org/mailman/options/python-3000/charles.merriam%40gmail.com > _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
