[Qt-interest] strange qFuzzyCompare implementation

[Konrad Rosenbaum]

On Monday 13 April 2009, Reinhardt Behm wrote:
> Your "solution" is totally unportable because your assumptions about the
> representation of float numbers will only be correct on a x86 evironment.

Wrong. It is designed to work with IEEE 754 floats, which are stored in the 
same endianess as integers on this platform.

Works on x86, x64, and most big-endian systems. Probably most systems.

> And even there some compiler implementation might store floats
> differently.

Very unlikely.

> Try running it on e.g. an ARM platform and it will not word 
> at all.

I doubt that. (Until someone shows me program output from an actual ARM or 
ARM emulator. Please include the sizeof output of the chosen types.)

> This is no solution for a multiplatform toolkit like Qt. 

Besides my doubts for your pessimism, it is still not a good solution for 
cross-platform, since it needs platform dependent adjustments for endianess 
and the used int types. On some platforms it might(!) not work at all. 

Not that Qt would not already contain quite a few platform dependent header 
files (guess where stuff like qint32 comes from), but this might be too 
much.

> Besides it is bad programming style to rely on such undocumented
> behaviour.

The behaviour is documented in IEEE 754.


	Konrad

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