http://qs321.pair.com?node_id=143135


in reply to Array sort - kind of...

@array = sort { $a->[2] <=> $b->[2] } @array

But, you say you want to find the $i with the smallest z value. It's best to _not_ sort for that: 

my $min_i = 0;
foreach my $i (1..$#array) {
  $min_i = $i if $array[$i]->[2] < $array[$min_i]->[2];
}

[download]

(update: Oops. Forgot the ->[2].)

This should be signifigantly faster, especially when @array gets large...

Replies are listed 'Best First'.
Re: Re: Array sort - kind of...
by Anonymous Monk on Feb 04, 2002 at 02:07 UTC
    This isn't relevant at all for the issue, but I have a question: Why do you choose to have $i over $_? There is a slight performance improvement when the loop is entered, but still...
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      True, he could have it written it in such a way to minimize a bunch of the minor overheads of the loop construct.

      Thus 

      my $min_i = 0;
foreach my $i (1..$#array) {
  $min_i = $i if $array[$i]->[2] < $array[$min_i]->[2];
}

      [download]
      becomes 
      my $index=0;
$array[$_][2]<$array[$index][2] && ($index=$_)
   foreach 1..$#array;

      [download]
      But I'm so sure its easier to understand...

      ;-)

      Yves / DeMerphq
      --
      When to use Prototypes?

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[d/l]
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        Wouldn't this eliminate more of the overhead?
        my ($min, $min_i) = ($array[0]->[2], 0);

foreach my $i (1..$#array) {

  ($min, $min_i) = ($array[$i]->[2], $i) if $array[$i]->[2] < $min;
}

        [download]


          p
[reply]
[d/l]
      I find it clearer, since smitz referred to $i as the index to the array in the question and since $i, $j, etc. make me think "this is a counter variable" when I see them.
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