in reply to Finding unique elements in an array

It's in perlfaq4 "How can I remove duplicate elements from a list or array?".

Also, your line 19: 

{push @out,$a;} unless (defined($lasta) && ($lasta eq $a));

[download]
gives me a syntax error.

Replies are listed 'Best First'.
Re^2: Finding unique elements in an array
by Joost (Canon) on Mar 15, 2005 at 13:10 UTC
[reply]
[d/l]

      But that's not what uniq does: it only removes elements that are the same as the previous element in the list.
      Are you looking at a different version of perlfaq4? My perl 5.8.6 version of perlfaq 4 "How can I remove duplicate elements from a list or array" gives 5 options, option a) of which states:
      If @in is sorted, and you want @out to be sorted: (this assumes all true values in the array) 
          $prev = "not equal to $in[0]";
    @out = grep($_ ne $prev && ($prev = $_, 1), @in);

      [download]
      This is nice in that it doesn't use much extra memory, simulating uniq(1)'s behavior of removing only adjacent duplicates. The ``, 1'' guarantees that the expression is true (so that grep picks it up) even if the $_ is 0, ``'', or undef.
[reply]
[d/l]
        I thought it looked like a nice job for List::Util, but it requires too much fiddling to make it come up with an array, so it's not really elegant. (The reason I wanted to try it is that it pre-loads $prev.) 
        use List::Util 'reduce';

sub uniq {
    return @{;reduce {ref $a or $a=[$a]; push @$a, $b if $b ne $a->[-1
+]; $a} @_};
};

        [download]
        So it looks like grep is the right tool.

        Update: This is a little shorter version with grep: 

        sub uniq {
    return @_ ? @_[0, grep {$_[$_] ne $_[$_-1]} 1..$#_] : ();
};

        [download]
        Caution: Contents may have been coded under pressure.
[reply]
[d/l]
[select]
[reply]

In Section Seekers of Perl Wisdom