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Implementation of qFuzzyCompare and zero values
j1elo last edited by
I'm using qFuzzyCompare(a, b) in order to handle all floating point comparisons, but it has severe limitations when a or b may be zero.
Somewhere in the docs it is recommended to add +1 to the values, but this is not a really useful suggestion because some of the values might be -1.0, resulting in 0.0 after the addition.
So far, in each file which needs to perform floating point comparisons, I'm using the following macro:
#include <QtGlobal> // qMax, qMin, qFuzzyCompare
#define qFuzzyCompare(a, b) (qFuzzyIsNull(a) && qFuzzyIsNull(b)) || qFuzzyCompare((a), (b))
But instead of ad-hoc workarounds, IMHO this caveat should be fixed straight in the implementation of the qFuzzyCompare() function. A really old bug report already exists: "QTBUG-16819":https://bugreports.qt-project.org/browse/QTBUG-16819 it is open but it seems that discussion ended on 2011 for some reason.
Could anyone add a bit more on this subject?
Hmm... I'm not familiar with this issue, but it does look like something that could be handled better by the library itself.
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tonyorourke last edited by
My guess is the good folks at Qt aren't interested because the good folks at Qt don't use qFuzzyCompare themselves; instead, they favour a set of 'qFsk...' routines which you'll find here -
(or somewhere like it, depending on where your Qt3d source code is)
The routines you find there should solve your problems.