in reply to Re^2: setting PERL_PERTURB_KEYS & PERL_HASH_SEED in a perl file
in thread setting PERL_PERTURB_KEYS & PERL_HASH_SEED in a perl file

Thx Everyone.

The solution you gave indeed work.

exec( $^X, $0, @ARGV );

I was sure that whatever written inside a BEGIN statement is hapannig before everything else, so I'm not sure why my first attempt did't wok

Isn't there a way to solve that without recalling the script again?

By the way, I don't rely on hash to be sorted, but in this case I did my sort base on the values and not the keys.

Since the values might be equal I got inconsistent printing while in earlier perl version the printing was consistent.

Thx

Guy

  • Comment on Re^3: setting PERL_PERTURB_KEYS & PERL_HASH_SEED in a perl file

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Re^4: setting PERL_PERTURB_KEYS & PERL_HASH_SEED in a perl file
by haukex (Archbishop) on Jul 18, 2016 at 12:57 UTC

    Hi gravid,

    Could you show a short example of the kind of sort you're doing (some sample input data, brief code and expected output)? I'm almost certain there's a better solution than messing with Perl's internal hash settings and re-starting the interpreter.

    Regards,
    -- Hauke D

[reply]

      Hi,

      Lets say we have this hash:

      $hash{a} = 0;
$hash{b} = 1;
$hash{c} = 0;
$hash{d} = 3;

      [download]

      The expected output is:

      a = 0
c = 0
b = 1
d = 3

      [download]

      or

      c = 0
a = 0
b = 1
d = 3

      [download]

      (note how 'a' & 'c' are switched)

      Both are correct!

      However, for consistency, I rather have always the same output.

      The code that I'm using is:

      foreach my $k ( sort { $hash{$a} <=> $hash{$b}  } keys %hash  ) {
    print "$k = $hash{$k}\n";
}

      [download]

      Thx

      Guy

[reply]
[d/l]
[select]
        sort { $hash{$a} <=> $hash{$b} || $a cmp $b }

        [download]
        I was sure that whatever written inside a BEGIN statement is hapannig before everything else, so I'm not sure why my first attempt did't wok

        So you thought that the Perl code in a BEGIN block would be run by the perl interpreter before the perl interpreter was initialized? Surely it is not hard to see why that is not the case.

        - tye        

[reply]
[d/l]

        Hi gravid,

        Yep, there's a better solution than messing with Perl's internals :-)

        my %hash = ( a=>0, b=>1, c=>0, d=>3 );
foreach my $k ( sort { $hash{$a} <=> $hash{$b} or $a cmp $b } keys %ha
+sh  ) {
    print "$k = $hash{$k}\n";
}

        [download]

        Always outputs:

        a = 0
c = 0
b = 1
d = 3

        [download]

        Background: If the comparison of the values (<=>) shows they are equal it returns zero, so then the second part of the or expression is evaluated, comparing the keys.

        Update: See the multi-field sort in How do I sort an array by (anything)? That FAQ answer also references this article: Far More Than Everything You've Ever Wanted to Know About Sorting

        Hope this helps,
        -- Hauke D

[reply]
[d/l]
[select]

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