RE: [FWP] sifting

["Larry Rosler" <lr@hpl.hp.com>]

> From: Jeff Pinyan [mailto:jeffp@crusoe.net]
> Sent: Wednesday, April 12, 2000 10:34
> To: fwp@technofile.org
> Subject: Re: [FWP] sifting
>
>
> On Apr 12, Jeff Pinyan said:
>
> >  sub grep_sift {
> >    my @sifted = ();
> >    my @list = @{ shift() };
> >
> >    for my $re (@_) {
> >      my @normal;
> >      push @sifted, grep {
> >        ($_ =~ $re) ? 1 : do { push(@normal, $_), 0 }
> >      } @list;
> >      @list = @normal;
> >    }
> >
> >    return (@sifted,@list);
> >  }
>
> I sped up grep-sift, and now it seems to run consistently
> faster.  I'll
> keep testing though.
>
>   http://www.pobox.com/~japhy/DALnet-perl/sift/

This should be faster for your loop, as it avoids copying the remaining
list on each pass:

  for my $re (@_) {
    for (my $i = 0; $i < @list; ++$i) {
        $list[$i] =~ /$re/ and push @sifted, splice @list, $i--, 1;
    }
  }

--
Larry Rosler
Hewlett-Packard Laboratories
http://www.hpl.hp.com/personal/Larry_Rosler/
lr@hpl.hp.com



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