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Re^3: Numeric sorting WITHOUT <=>

by ikegami (Pope)
on Oct 10, 2012 at 18:25 UTC ( #998282=note: print w/replies, xml ) Need Help??

in reply to Re^2: Numeric sorting WITHOUT <=>
in thread Numeric sorting WITHOUT <=>

sort uses mergesort by default, not quicksort. That could be a more appropriate choice?

Your last snippet has a memory leak.

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Re^4: Numeric sorting WITHOUT <=>
by tobyink (Abbot) on Oct 10, 2012 at 21:43 UTC

    Mergesort is more complex to implement I think, though not massively so. Perl did once use quicksort, but it was changed in 5.8. The old sorting algorithm can be enabled using:

    use sort '_quicksort';

    Memory leak... indeed. Is it too early to be getting sick of pre-5.16 Perls? In practice you'd probably give the sub a name so this wouldn't be an issue.

    perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'
      Actually, a naïve merge sort is dead simple. Quite possibly the easiest to explain, too.
      sub mergesort { return $_[0] if @_ == 1; my $i = int( @_ / 2 ); my @a = mergesort(@_[0..$i-1]); my @b = mergesort(@_[$i..$#_]); my @sorted; while (@a && @b) { if ($a[0] < $b[0]) { push @sorted, shift(@a); } elsif ($b[0] < $a[0]) { push @sorted, shift(@b); } else { push @sorted, shift(@a), shift(@b); } } return ( @sorted, @a, @b ); }

      lol! I got two 5.8.8 question this week. It'll be a while before it's ok to be sick of 5.14.

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