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It doesn't work. Well, it does work, but only if the XFORM routine returns a string of the same length for every item. Otherwise, the sorting could turn out wrong.

I've made a very contrived example, containing lots of null bytes, but actually, if you have a sufficiently large amount of array items, you can get the same effect on other bytes as well.

Let me demonstrate the effect by sorting a number of variable length strings as is, and with the packed index appended. As is shown, the sorted results are not in the same order at all.

use Data::Dumper; $Data::Dumper::Useqq = 1; my @data = map "\0" x $_, 0 .. 5; print Dumper [ sort @data ], [ sort map pack("a*N", $data[$_], $_), 0 .. $#data ];
Result:
$VAR1 = [ "", "\0", "\0\0", "\0\0\0", "\0\0\0\0", "\0\0\0\0\0" ]; $VAR2 = [ "\0\0\0\0", "\0\0\0\0\0\0\0\0\5", "\0\0\0\0\0\0\0\4", "\0\0\0\0\0\0\3", "\0\0\0\0\0\2", "\0\0\0\0\1" ];

In reply to Re: fast, flexible, stable sort by bart
in thread fast, flexible, stable sort by tye

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