On Monday 21 Dec 2009 18:09:32 Bryan R Harris wrote:
> > Wagner, David --- Senior Programmer Analyst --- CFS wrote:
> >> You pass as a refernce as ni
> >> called_sub(\...@d);
> >> Now when you update, you are updating @d and not a copy.
> >
> > No need to use a reference for that:
> >
> > perl -wle '
> >
> > sub inc{ ++$_ for @_ }
> >
> > my @x = 1 .. 5;
> >
> > inc @x;
> >
> > print "@x";
> > '
> > 2 3 4 5 6
>
> FYI, the reason we wanted a reference was because the data set might end up
> being huge.
>
> Uh, come to think of it, I'm surprised your script does what it does. I'd
> have thought that the changes made internal to inc would've stayed there
> since they're not being "returned". This bothers me a little...
>
@_ contains aliases to the variables. So you can do (untested):
<<<<<<<<<
sub modify_var
{
$_[0] += 100;
return;
}
my $x = 5;
modify_var($x);
# $x is now 105.
>>>>>>>>>
However, note that I consider tricks like that as a bad idea and prefer to use
references if I wish to do it. using << my $x = shift; >> or << my ($x) = @_;
>> will not keep the aliasing. That's how the Perl 5 implementation works.
Regards,
Shlomi Fish
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