Re^3: understanding closures

[dragonchild]

I was expecting this to print 0,1,11,12,13 - on the grounds that my two anonymous subs would be saving the same reference to the lexical ($count). But it seems to have merged two of my adds in together!! Help.

Your closures are correct. However, you're confused about something else. $count++ will return the value of $count, then add 1 to it. $count+=10 will add 10 to count, then return the value of $count.

Try the following:

my $count = 0;
sub make_two_counters {
    return sub{ $count++ }, sub{ $count+=10 }
}

my ($counter_plus_one, $counter_plus_ten) = make_two_counters();
print $counter_plus_one->() . " ($count)\n";
print $counter_plus_one->() . " ($count)\n";
print $counter_plus_ten->() . " ($count)\n";
print $counter_plus_one->() . " ($count)\n";
print $counter_plus_one->() . " ($count)\n";

__OUTPUT__

0 (1)
1 (2)
12 (12)
12 (13)
13 (14)

Does that help?