SPUG: Fw: Uniq in perl

[Bill Alford]

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
> > >
> > >
> >
> >  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> >      POST TO: spug-list at pm.org       PROBLEMS: owner-spug-list at pm.org
> >       Subscriptions; Email to majordomo at pm.org:  ACTION  LIST  EMAIL
> >   Replace ACTION by subscribe or unsubscribe, EMAIL by your Email-address
> >  For daily traffic, use spug-list for LIST ;  for weekly, spug-list-digest
> >   Seattle Perl Users Group (SPUG) Home Page: http://www.halcyon.com/spug/
> 
> 
>  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>      POST TO: spug-list at pm.org       PROBLEMS: owner-spug-list at pm.org
>       Subscriptions; Email to majordomo at pm.org:  ACTION  LIST  EMAIL
>   Replace ACTION by subscribe or unsubscribe, EMAIL by your Email-address
>  For daily traffic, use spug-list for LIST ;  for weekly, spug-list-digest
>   Seattle Perl Users Group (SPUG) Home Page: http://www.halcyon.com/spug/
> 
> 


 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     POST TO: spug-list at pm.org       PROBLEMS: owner-spug-list at pm.org
      Subscriptions; Email to majordomo at pm.org:  ACTION  LIST  EMAIL
  Replace ACTION by subscribe or unsubscribe, EMAIL by your Email-address
 For daily traffic, use spug-list for LIST ;  for weekly, spug-list-digest
  Seattle Perl Users Group (SPUG) Home Page: http://www.halcyon.com/spug/