Calculator: 49,8-2,1=

htc_tattoo · 28 Oct 2018, 21:29

I was astonished when i calculated
49.8-2.1=47.699999999999996
I learned different in school. Yes, it's true, i could have calculated in my head. But i was lazy...
Calculator Version 2.3.4 i used.

guru · 28 Oct 2018, 23:22

Same error with OTA3.

dobey · 29 Oct 2018, 01:26

Please open an issue at https://github.com/ubports/ubuntu-touch/issues about the problem. The forum is not an issue tracker, so reporting problems here is not especially helpful.

guru · 29 Oct 2018, 05:41

https://github.com/ubports/ubuntu-touch/issues/940

dtarrant · 2 Nov 2018, 10:07

Seems to be fixed now: 49.8-2.1=47.7!

flohack · 3 Nov 2018, 21:36

When you would read a bit about this problem, it would be more clear to you: In contrast to integer numbers floating point numbers can almost never calculated precisely on any CPU / computer on the market.

If you are interested please read e.g. https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html - Its a bit inclined but explains a lot.

Bottom line, what you learned in school is right, and the CPU lied to you. Unfortunately it did not round the number so to hide the lie

We fixed it by updating math.js from a 2015 version to 2018. 3 years pass and the lie seems to be perfect now

BR

htc_tattoo · 4 Nov 2018, 08:10

Thanks a lot for fixing this! Although it's just a funny small problem, fixing this tiny bugs also lead to a better system.
If i compare UT today with 1 or 2 years ago it improved really a lot! Stability, features and speed!