SPUG: Fw: Uniq in perl
Bill Alford
billa at willapabay.org
Mon Mar 19 17:58:05 CST 2001
All the solutions I've seen so far look good for treating the list as a
set (I may have missed one that didn't). But, from the uniq man page:
Discard all but one of successive identical lines from
INPUT (or standard input), writing to OUTPUT (or standard
output).
It looks like that's what's happening below.
Here's what I can come up with (not tested and a little verbose, but I
like verbose :) :
sub uniq {
if (! @_) {
return @_; # for the empty set case
}
my $last = shift;
my @result = ( $last );
my $cur;
foreach $cur ( @_ ) {
# assuming string input
if ($cur ne $last) {
$last = $cur;
push(@result,$cur);
}
}
return @result;
}
On Mon, 19 Mar 2001, jeff saenz wrote:
> What if you convert the array values to hash keys and let the hash eliminate the
> duplicates? Something like:
>
> @hash{@array} = ();
> or maybe a map. but i think maps are inefficient. something like that.
>
> Richard Anderson wrote:
>
> > Does anyone have comments for Mike?
> >
> > Richard Anderson, Ph.D. www.unixscripts.com
> > Perl / Oracle / Unix Richard.Anderson at raycosoft.com
> > Raycosoft, LLC Seattle, WA, USA
> > ----- Original Message -----
> > From: "Mike" <shivan at ici.net>
> > To: "Richard Anderson" <Richard.Anderson at raycosoft.com>
> > Sent: Friday, March 16, 2001 2:12 PM
> > Subject: Uniq in perl
> >
> > > This is something I had sitting around. I didn't write it. Its a subroutine
> > > that uniqs an array. I was just wondering if this is the best way to do it
> > > or if anyone has any thing better. Thanks
> > >
> > >
> > > ## Usage: &uniq( \@ARRAY );
> > > sub uniq {
> > > my (@uwork, @unew, $uname);
> > > @uwork = @{$_[0]};
> > > @uwork = sort( @uwork );
> > > @unew = ( shift @uwork );
> > >
> > > foreach $uname ( @uwork ) {
> > > @unew=( @unew, $uname) if ( $uname ne $unew[ -1 ] );
> > > }
> > >
> > > @{$_[0]}=@unew;
> > > }
> > >
> > > :wq
> > >
> > >
> >
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