From: Richard Lee <[EMAIL PROTECTED]>
> trying to understand closure and callback(bit over my head but)
>
> while I think i grasp most of the ideas from below program.. I don't
> think I understand why ( ) is needed in
>
> my $sum = $subs{$_}{GETTER}->( );
Because $subs{$_}{GETTER} is a subroutine reference and you need to
"dereference" it. And just like you can use either
${$arrayref}[1] or $arrayref->[1] to dereference a reference to an
array you can use either &{$subref}(1) or $subref->(1) to dereference
a reference to a subroutine (that is to call the referenced
subroutine). In your particular case you just do not need to pass any
parameters so it would be $subs{$_}{GETTER}->( ) or
&{$subs{$_}{GETTER}}.
HTH, Jenda
P.S.: Of course the example is a little convoluted. If you did not
want to use a global variable you could do something like this:
#!/usr/bin/perl
use warnings;
use strict;
use File::Find;
sub sum_size_into {
my $total_size = shift;
die "sum_size_into() parameter must be a scalar ref!" unless
ref($total_size) eq 'SCALAR';
return sub { $$total_size += -s if -f };
}
for my $dir ( qw(bin lib man) ) {
my $sum = 0;
find( sum_size_into(\$sum) , $dir);
print "$dir has $sum bytes\n";
}
That is instead of generating a callback and a getter, you specify
where should the callback store the result.
Or, since the action is fairly simple and there is little need for a
callback generator:
use warnings;
use strict;
use File::Find;
for my $dir ( qw(bin lib man) ) {
my $sum = 0;
find( sub { $sum += -s if -f }, $dir);
print "$dir has $sum bytes\n";
}
===== [EMAIL PROTECTED] === http://Jenda.Krynicky.cz =====
When it comes to wine, women and song, wizards are allowed
to get drunk and croon as much as they like.
-- Terry Pratchett in Sourcery
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