Funny story of how Perl people can clear an array.

1. There’s more
than one way
to empty it

2. Perlish
more-than-one-way

3. We hired
Delphi/SQL
programmer

4. as a Perl developer

5. Good programmer
writes good code
in every language

6. But lots of fun

7. sub clear{
my $template = shift @args;
@{$self->{tokens}} = ();
foreach (map {$_->{name}} @{$template->{si}}){
while (my $r = shift @{$self->{$_}->{res}}){}
}
}

8. Che cazzo di..?*
* WTF? (Italian)

9. sub clear{
my $template = shift @args;
@{$self->{tokens}} = ();
foreach (map {$_->{name}} @{$template->{si}}){
while (my $r = shift @{$self->{$_}->{res}}){}
}
}
A subroutine to make an object empty

10. sub clear{
my $template = shift @args;
@{$self->{tokens}} = ();
foreach (map {$_->{name}} @{$template->{si}}){
while (my $r = shift @{$self->{$_}->{res}}){}
}
}
Note this

11. Posted that piece to
Moscow.pm mailing list

12. And we bacame crazy

13. 1
while (my $r = shift @a) {}

14. 2
splice @a;

15. 3
delete(@a[0..$#a]);

16. 4
grep {shift @a} @a;

17. 5
@a = ();

18. 5
@a = ();
Boring!

19. 6
undef @a;

20. ccn@ccn-laptop ~
$ perl -le 'my @a=(1,2,3); while(my $r =
shift @a){}; print @a'
ccn@ccn-laptop ~
$ perl -le 'my @a=(0,1,2,3); while(my $r
= shift @a){}; print @a'
123

21. 7
while(defined(my $r = shift @a))
{}

22. ccn@ccn-laptop ~
$ perl -le 'my @a=(undef,1,2,3);while
(defined(my $r=shift @a)){};print @a'
123

23. Doesn’t work

24. Let’s make it
useful

25. $str = "abcc{0}def";
@a = split //, $str;
$c++ while(shift @a);
say $c - 1;
Calculate zero-ending string length

26. 8
while(chomp $str) {};

27. 9
while(@a) {shift @a}

28. 10
shift @a while @a;
Much better!

29. 11
shift @a while @a and die;

30. 12
shift @a while scalar @a;

31. 13
$#a = -1
Who remembers?!

32. use Benchmark qw(:all :hireswallclock);
my $size = 1000; Be
cmpthese timethese -3, { nc
'@a = ...' => sub { my @a = (('test')x$size); h m
return; }, ar
'undef @a' => sub { my @a = (('test')x$size); undef @a; ke
return; }, d
'@a=()' => sub { my @a = (('test')x$size); @a = ();
return; },
'splice @a' => sub { my @a = (('test')x$size); splice @a;
return; },
'$#a = -1' => sub { my @a = (('test')x$size); $#a = -1;
return; },
'shift @a while @a' => sub { my @a = (('test')x$size); shift @a
while @a; return; },
'delete @a[0..#$a]' => sub { my @a = (('test')x$size);
delete(@a[0..$#a]); return; },
};
при $size=1000;
shift @a while @a 2642/s -- -22% -44%
-44% -45% -45% -45%
delete @a[0..#$a] 3376/s 28% -- -28%
-29% -29% -30% -30%
splice @a 4722/s 79% 40% --
-0% -1% -2% -2%

33. TIMTOWTDI or die;
Andrew Shitov
talks.shitov.ru | andy@shitov.ru