in reply to Re^3: Sort undef
in thread Sort undef

It would seem that deaccent()would modify the data to a sub-255 value, leaving a single 255 in the Schwartian Transform as a viable sort max key -- as noted above, this should be proven before deployed.

As to your other note, Unicode characters "above 255" are actually multi-byte sequences whose individual bytes still cannot exceed the architectural limitation of chr(255) so I question that perceived vulnerability.

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Re^5: Sort undef
by Anonymous Monk on Jun 17, 2017 at 03:50 UTC
    Perl strings are sequences of Unicode code points, not sequences of bytes. (Well, I think they're stored internally as plain bytes if possible.) 
    use Encode qw( encode_utf8 );
my $x = chr(1 << 63);
print length($x), "\n";
print length(encode_utf8($x)), "\n";
print "yep\n" if $x gt chr(255);

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    Output: 
    Use of code point 0x8000000000000000 is deprecated; the permissible ma
+x is 0x7FFFFFFFFFFFFFFF at foo line 2.
1
13
yep

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      Going back to my attitude when I was a C programmer: It pays to know how your compiler thinks. (Needs adjustment for application to modern use of Perl, but the sentiment is the same.)

      Adding/replacing these three lines into my original script above:

      use Encode qw( encode_utf8 );
my $x = chr(1 << 63);
my @Unsorted = ( 'Dog', 'Cat', 'Bird', undef, $x, 'Elephant', undef, '
+Lizard' );

      [download]

      Yields:

      S:\Steve\Dev\PerlMonks\P-2017-06-12@0734-sort-undef>perl .\sort011.pl
----------------------------------------------------------------------
+---------
Original:
----------------------------------------------------------------------
+---------
Dog
Cat
Bird
(undef)
Wide character in print at .\sort011.pl line 58.
 ÇêÇÇÇÇÇÇÇÇÇÇ
Elephant
(undef)
Lizard
----------------------------------------------------------------------
+---------
----------------------------------------------------------------------
+---------
Custom Sort:
----------------------------------------------------------------------
+---------
Bird
Cat
Dog
Elephant
Lizard
(undef)
(undef)
Wide character in print at .\sort011.pl line 58.
 ÇêÇÇÇÇÇÇÇÇÇÇ
----------------------------------------------------------------------
+---------

S:\Steve\Dev\PerlMonks\P-2017-06-12@0734-sort-undef>

      [download]

      A string of chr(255)bytes longer than the longest item in the original array still fails to sort to the bottom; knowing that Unicode characters are stored differently than old-fashioned ASCII strings empowers the Perl programmer to make a better choice.

      Thank you for the information!

      I'd upvote the post, but there isn't any point, as it's Anonymous Monk.

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