[Interest] JS numbers to qint64
Andrew Ialacci
andrew at dkai.dk
Wed Jul 12 17:09:37 CEST 2017
Any fancy math, do in C++ with a floating-point library and pass to JS/QML as a string purely for the intent of displaying in the UI. The only exception should be for layout / item positioning. There are single JS file floating point libs but… Use C++ :P
Disclaimer: This is just a suggestion and could likely be wrong. Definitely defer to anything anyone else suggests on this mailing list as they are all smarter than me!
On 7/12/17, 10:55 AM, "Interest on behalf of Thiago Macieira" <interest-bounces+andrew=dkai.dk at qt-project.org on behalf of thiago.macieira at intel.com> wrote:
On quarta-feira, 12 de julho de 2017 02:53:39 PDT Shantanu Tushar wrote:
> qml: Opening 5762702576189441
> Opening 5762702576189442
>
> As you can see the number changes. What am I doing wrong?
Expecting JS numbers to be precise.
Remember that in JavaScript, numbers are actually double-precision floating
point. They are lossy.
They can represent with fidelity only in the range ±2^53. Yours is inside the
range (only just!) but a simple manipulation of it could throw it outside for
a while.
I recommend staying well away from the limits. Like limiting to 32 bits.
--
Thiago Macieira - thiago.macieira (AT) intel.com
Software Architect - Intel Open Source Technology Center
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