On Sun, 2023-04-16 at 10:50 -0700, Nils Bruin wrote: > > That's a facetious example that sticks to values that can be exactly > represented in binary floats. These identities don't hold generally: > > sage: 49*(1.0/49) == ZZ(1) > False > > (it depends on your working precision if rounding makes this come out as an > exact match or not, but at 53 bits this one fails to give equality. In all > cases, there are values where this breaks; necessarily)
I didn't make that example up to make a point, it's a real problem I reported ~15 years ago in undergrad. And the fact that it's an easy case only makes it *more* surprising that sage doesn't handle it. We don't need a perfect solution to get it right most of the time. How often does someone type 1/49 = 0.02040816326530612... into a matrix? But Sage actually knows that number too: $ sage -python Python 3.11.2 (main, Mar 16 2023, 15:12:59) [GCC 12.2.1 20230121] on linux Type "help", "copyright", "credits" or "license" for more information. >>> from sage.all import * >>> QQ(0.02040816326530612) 1/49 -- 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/b2e128ee0d91cc0f8f05fd160e07d23da1f0714f.camel%40orlitzky.com.
