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

Re^3: why need my in a foreach loop?

by szabgab (Priest)
on Nov 28, 2010 at 18:37 UTC ( #874128=note: print w/ replies, xml ) Need Help??


in reply to Re^2: why need my in a foreach loop?
in thread why need my in a foreach loop?

The foreach loop always works with an alias. IMHO the variable is never connected to anything outside the for loop so the values never "leak" out of the loop. If I am mistaken, please give an example when that variable is connected to something else as well.


Comment on Re^3: why need my in a foreach loop?
Re^4: why need my in a foreach loop?
by ikegami (Pope) on Nov 28, 2010 at 18:52 UTC
    I've already showed when it makes a difference.
      Oh, apparently I did not read your example in detail. Interesting example. Now I understand how the "my" makes a difference there. Thanks.

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

        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

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://874128]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others meditating upon the Monastery: (13)
As of 2014-07-22 13:29 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    My favorite superfluous repetitious redundant duplicative phrase is:









    Results (113 votes), past polls