[fpc-devel] Sorting tests

Ondrej Pokorny lazarus at kluug.net
Tue Nov 29 11:39:06 CET 2022

Am 29.11.2022 um 11:08 schrieb Sven Barth via fpc-devel:
> J. Gareth Moreton via fpc-devel <fpc-devel at lists.freepascal.org> 
> schrieb am Di., 29. Nov. 2022, 10:09:
>     Surely that's a bug in the comparison functions that should be
>     fixed and
>     not something that can be blamed on introsort.  If a comparison
>     function
>     is faulty, then pretty nuch any sorting algorithm can be
>     considered to
>     have unpredictable behaviour.
> This *can* be blamed on IntroSort, because Stability (order of equal 
> elements is kept) is an attribute of sorting algorithms and IntroSort 
> is *not* considered stable while QuickSort *can* be stable depending 
> on the implementation and ours *is*.

If for two elements [a, b] the comparison function returns
a<b=true and b<a=true

then the problem is not in stability or any other feature of the sorting 
algorithm but in the comparison function indeed. Or am I missing something?

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