Re^2: to avoid redundacy in a file

[tadman]

To avoid redundancy in your code, you could do this:

my %seen;

while (<>)
{
     next if ($seen{$_}++);
     print;
}

You can do it in one shot, so you might as well. Note that this code eliminates all duplicate lines, not just repeated ones. If you want to just ditch repeats, use this:

my $last;

while (<>)
{
     next if ($_ eq $last);
     $last = $_;
     print;
}

Thus lines "A A A B B B A A C C" will be "A B A C" not "A B C" as in the previous bit.

[Aristotle]

You can do it in one shot, so you might as well.

That makes your second snippet

my $prev;

while (<>) {
    next if ($_ eq $prev);
    print $prev = $_;
}

:^)

Wait, we can shorten that..

my $prev;

while (<>) {
    print $prev = $_ unless $_ eq $prev;
}

Hmm..

my $prev;
$_ ne $prev and print $prev = $_ while <>;

Err.. sorry, got carried away for a second.. Perl is just too seductive. Sigh. :-)

Makeshifts last the longest.

[tadman]

I was going to condense it down to a single line:

% perl -ne '$p ne$_&&print;$p=$_' ...