On Thu, Jan 28, 2021 at 10:21 AM Dima Pasechnik <dimp...@gmail.com> wrote: > > On Thu, Jan 28, 2021 at 8:33 AM Vincent Delecroix > <20100.delecr...@gmail.com> wrote: > > > > I would say, better to avoid it. That is a personal comment. > > > > Vincent > > > > Le 27/01/2021 à 18:48, G. M.-S. a écrit : > > > So if I understand you well, "x in P" should not be used for serious work? > > > > > > Guillermo > > > > > > On Wed, 27 Jan 2021 at 08:55, Vincent Delecroix > > > <20100.delecr...@gmail.com> > > > wrote: > > > > > >> Oups, I forgot to copy all the relevant input > > >> > > >> sage: a = 1.9999999999999999 > > >> > > >> Vincent > > >> > > >> Le 26/01/2021 à 19:38, G. M.-S. a écrit : > > >>> Just out of curiosity: What is "a"? > > >>> > > >>> Guillermo > > >>> > > >>> On Tue, 26 Jan 2021 at 09:29, Vincent Delecroix < > > >> 20100.delecr...@gmail.com> > > >>> wrote: > > >>>> > > >>>> And what should be thought about "4.0 in ZZ" ? > > >>>> > > >>>> Even more fun > > >>>> > > >>>> sage: a in ZZ > > >>>> False > > >>>> sage: 4 / a in ZZ > > >>>> False > > >>>> sage: 4.0 / a in ZZ > > >>>> True > > >>>> > > >>>> Does Sage even have any clear specification for "x in P"? > > Certainly. This is just Python: > https://docs.python.org/3/reference/expressions.html#membership-test-operations > > Specifically, you can explore how "in" is implemented for a concrete > class P by instpecting > > P.__contains__?? > > E.g. to get an idea about puzzling behaviour of ZZ look at (very short) code > in > ZZ.__contains__?? > > I don't see why you should avoid it. (You can avoid Python/Sage > completely, surely, but this is just Python > code, there is no weird magic there)
tl;dr. in partiular, t in ZZ whenever ZZ(t) succeeds. 4.0/a is a different floating point number to 4/a, and so YMMV. > > > > > >>>> > > >>>> Concerning input that are of the wrong type, it is common > > >>>> in Python (?) to just throw error > > >>>> > > >>>> >>> list(range(4)) > > >>>> [0, 1, 2, 3] > > >>>> >>> list(range(4.0)) > > >>>> Traceback (most recent call last): > > >>>> ... > > >>>> TypeError: 'float' object cannot be interpreted as an integer > > >>>> > > >>>> Vincent > > >> > > > > > > > -- > > You received this message because you are subscribed to the Google Groups > > "sage-support" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to sage-support+unsubscr...@googlegroups.com. > > To view this discussion on the web visit > > https://groups.google.com/d/msgid/sage-support/693740a1-0110-1c28-eeda-a3635b06e36c%40gmail.com. -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-support/CAAWYfq0vCnsa%3DQwPPkgtr92E3wZj98Tha1Fhd7PfQnjB8mfyVw%40mail.gmail.com.
