in reply to Whether to use local()

"...why would you go to the trouble of using local if you aren't trying to keep some private value ... somewhere?"

Personally, i wouldn't. But the caveat depends on what kind of program you are writing.

When i write utility scripts, avoiding global variables is usually a waste of typing to me - i use them. Keep in mind that i do have a CS degree and my professors would never allow us to use globals ever anywhere! I appreciated that, but now that i understand the rules, i can break them. >:)

Let's say that i am writing a larger program. Then i would strongly consider OO. OO is good for eliminating globals, because you instead have accessor methods (considering, of course, that it is good OO).

Finally, local vs. my - in my limited experience with local, i only use it to erase Perl's built-in variables, like $/ for slurp mode (thanks again tye!): 

my $slurp = do {local $/; <FH>};

[download]
All of my variables are declared with my. To be honest, i am still missing the picture of when you need our.

Hope this helps :)

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

Replies are listed 'Best First'.
Re: (jeffa) Re: Whether to use local()
by tachyon (Chancellor) on Mar 15, 2002 at 19:25 UTC

    Does this snippet explain our for you jeffa ? 

    # comment use strict in and out
# use strict;

package Foo;
our $global = 'global ';
$not_so_global = 'not so global';

package Bar;
print "Full package name: ", $Foo::global, $Foo::not_so_global, "\n";
print "No package name:   ", $global, $not_so_global, "\n";

    [download]

    cheers

    tachyon

    s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

[reply]
[d/l]
      Ahhhh, i am starting to see now:
      • my declares a local variable which is not found in a package's symbol table
      • a local var does show up in the symbol table, but if you use strict, then you have to fully qualify the variable name (that is, prefix the package name)
      • our handles the strict vs. non-fully qualified local vars
      perrin pointed me to CPAN and the Devel::Symdump module. Here is another snippet to help explain: 
      #!/usr/bin/perl

#use strict;
use Devel::Symdump;

my $obj = Devel::Symdump->new('Foo');

print map {"$_\n"} $obj->scalars;

package Foo;

local $Foo::qualified;
local $unqualified;
our   $our;
my    $my;

      [download]
      Which (without use strict) produces this ouput : 
      Foo::qualified
Foo::our
Foo::unqualified
      If strict is turned on, then $unqualified will cause a compliation error. I think i get it now! :)

      Thank you tachyon, perrin, and also rob_au for pointing out What is it adding to my symbol table?.

      jeffa

      L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)
[reply]
[d/l]

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