On Sun, Apr 16, 2023 at 12:40 PM Michael Orlitzky <mich...@orlitzky.com> wrote: > > On Sat, 2023-04-15 at 19:11 -0700, Nils Bruin wrote: > > > > I fail to see what the reasonable expectations are here. As soon as you > > multiply by "0.5" you now have an "imprecise" result. When people learn to > > use a scientific calculator properly they are very quickly confronted with > > the reality that "dots in numbers" lead to arithmetic that isn't quite what > > we learn in the lower grades of primary school. > > It's reasonable to expect that multiplying by one won't cause a viable > alternative to Mathematica et al. to go bonkers. I haven't declared a > float variable, and I haven't type-cast anything to float. The > expression "0.5" is, a priori, quite equal to 1/2. Mathematica knows > it, my old Casio calculator knows it, and in fact, Sage knows it: > > sage: 2 * 0.5 == ZZ(1) > True > > We're pre-parsing the user's input, so there is an opportunity to do > the right thing. But instead, we silently convert 2*0.5 to float, and > then silently convert the entire matrix to a float matrix, on which > half the methods in sage are completely meaningless. > > > > Do you think we should have "B == A" return false? ... > > A more reasonably solution might be to have B.rank() return an error > > Yes, ultimately, I think it would be better to have a class hierarchy > that can distinguish between inexact rings where these operations are > meaningful and those where they're not. But these are Sage library > issues and that's not my main complaint. > > If you're writing python code, you should expect 2*0.5 to return a > float. But if you're learning linear algebra for the first time and > typing a matrix into the Sage notebook, typing 0.5 instead of 1/2 > should not ruin the entire assignment without so much as a warning.
perhaps the preparser should have an option to convert the floating point input into rationals. > > -- > You received this message because you are subscribed to the Google Groups > "sage-devel" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-devel+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sage-devel/caa19202f0a1dc1eef92dbab1df231efb1f2741c.camel%40orlitzky.com. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/CAAWYfq2k7ZbrmsMRXs%3DHhdrRzqQZUsE2ESsM9G34HA%2BU4f3nYw%40mail.gmail.com.
