Beefy Boxes and Bandwidth Generously Provided by pair Networks
Pathologically Eclectic Rubbish Lister

Re^6: why need my in a foreach loop? (Aliasing)

by LanX (Chancellor)
on Dec 08, 2010 at 13:00 UTC ( #876015=note: print w/ replies, xml ) Need Help??

in reply to Re^5: why need my in a foreach loop?
in thread why need my in a foreach loop?

Hi Gabor

>However I'd be interested to know in what case would you really want to write such code?

As already said my is much younger than foreach and it's consistent and backward compatible.

While looping over localized globals could also be done with an extra local $packvar=$lex_for_var, the aliasing effect of foreach can't be achieved in any other way in core Perl.

$\="\n"; our $foo; sub f { $foo++ } my ($a,$b,$c)=(0)x3; for $foo ($a,$b,$c) { f(); # increments $a,$b,$c } print ($a,$b,$c); #: 111 for my $foo ($a,$b,$c) { f(); # nada } print ($a,$b,$c); #: 111 for my $x ($a,$b,$c) { local $foo=$x; f(); # nada } print ($a,$b,$c); #: 111 { my $foo; sub g { $foo++ } for $foo ($a,$b,$c) { g(); # nada (irritatingly) } print ($a,$b,$c); #: 111 }

For a detailed discussion, see How do closures and variable scope (my,our,local) interact in perl?.

Cheers Rolf

UPDATE: expanded code, fixed typos

Comment on Re^6: why need my in a foreach loop? (Aliasing)
Select or Download Code

Log In?

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://876015]
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others chanting in the Monastery: (5)
As of 2016-04-30 07:32 GMT
Find Nodes?
    Voting Booth?
    :nehw tseb si esrever ni gnitirW

    Results (441 votes). Check out past polls.