[Development] Should QVariant be doing fuzzy comparisons on doubles?

[Allan Sandfeld Jensen]

On Monday 19 September 2016, Thiago Macieira wrote:
> On segunda-feira, 19 de setembro de 2016 21:21:01 PDT André Pönitz wrote:
> > On Mon, Sep 19, 2016 at 11:10:51AM -0700, Thiago Macieira wrote:
> > > Since this is a P3 and 5.8 hasn't been released, I will push the
> > > behaviour change to 5.8 and drop the fuzzy comparison.
> 
> https://codereview.qt-project.org/171452
> 
> > > > QVariant should not expose any numeric or conversion functionality
> > > > and *only* be used to store and retrieve data. Comparison/Ordering
> > > > should only be used and only be available to the degree needed to
> > > > fullfil basic container requirements. Everything else has bitten in
> > > > the past, and will necessarily continue to do so, and adding more
> > > > conceptually *wrong* features only digs deeper holes.
> > > 
> > > That I can't do.
> > 
> > That is understood.
> > 
> > I am not asking to remove existing functionality, just to not to add
> > "convenience" like
> > 
> >     QVariant v1 = char('a');
> >     QVariant v2 = QChar('a');
> >     QVariant v3 = QString("a");
> >     assert(v1 == v2 && v2 == v3 && v1 != v3);
> 
> It may already be too late.

It is, I am pretty sure we can't fix associativity, but another example is 
that  qvariant equality is not even commutative right now, in the example 
above v2 == v3, but v3 != v2

I had this patch for it two years ago:
https://codereview.qt-project.org/#/c/92850

`Allan