Remy Guo wrote:
hi all,
I've got a problem in following script:
sub A {
our %a;
$a{"fred"} = 1;
$a{"bella"} = 2;
...
}
sub B {
if ($fred != $a{"fred"}) {
print "fred failed.\n";
}
if ($bella != $a{"bella"} {
print "bella failed.\n";
}
}
The problem is, I made the hash %a in sub A but in sub B, the value in hash
%a is never read. The declaration "our" seems not effect.
Why?...
If fred is spending this much time with bella,
don't let wilma find out.
Consider this:
#!./perl
use warnings;
use strict;
A();
B();
BEGIN {
my %a;
my $fred = 0;
my $bella = 2;
sub A {
$a{"fred"} = 1;
$a{"bella"} = 2;
}
sub B {
if ($fred != $a{"fred"}) {
print "fred failed.\n";
}
if ($bella != $a{"bella"}) {
print "bella failed.\n";
}
}}
I'm demonstrating that you can enclose multiple
subroutines in one block, and share variables
between them. Your question was about %a, and
that is addressed. You never mentioned where
$fred and $bella are given their values, so I
included them, too. But in order to call A()
and B() before their blocks are defined, I had
to make the enclosing block a BEGIN block.
This is getting beyond the beginner stage, and
it's rare that you would do something like this,
but I think it's instructive to know, given your
question.
After you read all the docs about references :-),
read this about scoping:
http://perl.plover.com/FAQs/Namespaces.html
including note number 3.
Cheers,
Brad
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