I'd guard against splice() continually from the beginning of an array. I'd much rather call it from the end of the array. "But Jeff," you'd say, "what if the order of the hash references matters? You couldn't do: 
while (my ($a,$b,$c) = splice(@data, -3)) {
  push @hashrefs, { a => $a, b => $b, c => $c };
  pop @data;  # null field
}

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because then @hashrefs would be in reverse!" Yes, that's absolutely right. And it might be inefficient to reverse() the array when we're done with it, and it's also inefficient to keep unshift()ing to the array. So what possible efficient solution could I come up with to combine the splice() speed with the insertion speed?

Pre-extend the array! (Dun, dun, DUN!) 
my @hashrefs;
$#hashrefs = int(@data / 4);
my $i = $#hashrefs;
while (@data and my ($a,$b,$c) = splice(@data, -3)) {
  $hashrefs[$i--] = { a => $a, b => $b, c => $c };
  pop @data;
}

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What a sneaky trick I've done.

Update

Oops, used -4 above, when I meant -3. Thanks, jcwren.

Update

splice() will wig out when the array is empty. The while loop has been adjusted.

japhy -- Perl and Regex Hacker

In reply to Re: Re: Sort this data by japhy
in thread Sort this data by Anonymous Monk

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