I've finally started reading Object Oriented Perl by Damien Conway and am enjoying it tremendously. Taking some of his code, I use a closure to create a simple binary toggle (something similar was discussed in this node).

Pass the sub a positive integer, $x, and it returns an anonymous sub that automatically toggles between 1 and 0 every $x times it's accessed. The following snippet illustrates its use.

Update: Made a slight change so that $count could start at zero instead of negative one. I also liked extremely's use of the ternary ( w = x ? y : z ) operator to set $bit!

#!/usr/bin/perl -w
use strict;

my $cycle = initToggle( 3 );

for ( 1 .. 24 ) {
    print "$_\t" . &$cycle . "\n";
}

sub initToggle {
    my $limit = shift;
    my $count = 0;
    my $bit   = 0;
    unless ( $limit > 0 ) { die "initToggle() requires a positive argu
+ment\n" };

    return sub {
        $bit ^= 1 if $count++ % $limit == 0;
        return $bit;
    }
}

[download]

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RE: Easy binary toggle at fixed intervals
by extremely (Priest) on Oct 21, 2000 at 11:45 UTC
    Sexy! I likey a lot. Still, I had to tinker... 
    #!/usr/bin/perl -w
use strict;
my $cycle = initToggle( 3 );

for (1..24) {
   print "$_ " . &$cycle . "\n";
}

sub initToggle {
   my $limit = shift;
   die "initToggle() requires a non-zero integer\n" 
      if ($limit == 0 or int($limit) != $limit);
   my $count = -1;
   my $bit   = $limit >0 ? 0 : 1;
   $limit = abs($limit);
   return sub {
      $bit ^=1 if (++$count % $limit == 0);
      return $bit;
   }
}

    [download]

    Now you can flip the bit on creation and you check for initToggle ( 3.333 );

    --
    $you = new YOU;
    honk() if $you->love(perl)

[reply]
[d/l]

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