The document discusses various ways to clear or empty an array in Perl. It provides 14 different code examples of subroutines that can remove all elements from an array, such as using shift, splice, deleting indices, setting the last index to -1, and undefining the array. Benchmark tests on arrays with 1000 elements show that shift while the array is not empty and deleting indices have better performance than other approaches like undefining the array.

1. How to
clean an array

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. Wat de fuck is dat?

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. Bonus
my @a = qw(oh eh);
while (push(@a, shift @a)) {};
Endless sex loop

33. 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%

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