Yes, I fear users are attempting simplistic banking apps with floating point rounds. :( May explain where millions of my pennies went in my last android stock sale!
On Fri, May 24, 2019 at 1:55 PM Warren Young <[email protected]> wrote: > On May 24, 2019, at 7:10 AM, Jose Isaias Cabrera <[email protected]> > wrote: > > > > Dr. Richard Hipp, on Friday, May 24, 2019 08:44 AM, wrote... > >>> Dr. Hipp, how many more scenarios, where round gives the wrong answer, > >>> exist? Thanks. > >> > >> Consider these two queries: > >> > >> SELECT round(3.255,2); > >> SELECT round(3.2549999999999998,2); > >> > >> Do you expect them to give different answers? > > > > 3.26 > > 3.25 > > Go read this: https://www.floating-point-gui.de/ > > Then install this extension: > > https://chiselapp.com/user/lifepillar/repository/sqlite3decimal/index > > Having done both, you’ll know why SQLite does what it does, and will have > a solution for the problem where it matters. > > And it doesn’t always matter! Anything dealing in real-world > measurements, for example, generally doesn’t need more than 9 decimal > digits of precision, depending on the measuring instrument, which is more > than covered by an IEEE-754 double. Measurement instruments are not > absolutely precise: they have inherent inaccuracies, and electronic > instruments have drift and other characteristics that can prevent them from > giving the same answer given the same task. > > Since the measurement itself cannot be more precise than an IEEE-754 > double, any “error” in an answer computed from it is down in the noise > floor of the measurement. That is to say, two measurements taken > back-to-back might give the same or greater error. > > This is no accident. IEEE-754 was designed by people working in the > physical sciences, and they knew all of this when they designed it. It is > what it was designed *for*. > > What IEEE-754 was *not* designed for was discrete math, such as monetary > matters on scales smaller than a national economy. > _______________________________________________ > sqlite-users mailing list > [email protected] > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ sqlite-users mailing list [email protected] http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
