On Mon, Jan 10, 2005 at 12:28:44PM -0500, [EMAIL PROTECTED] wrote:
> I hate confusion, so I went to the source: perldoc perlsub, and here is
> what it had to say:
>
> The Perl model for function call and return values is simple: all
> functions are passed as parameters one single flat
> list of scalars, and all functions likewise return to their caller
> one single flat list of scalars. Any arrays or
> hashes in these call and return lists will collapse, losing their
> identities--but you may always use pass-by-reference
> instead to avoid this.
>
> In other words, perl passes arguments by copy, not reference.
This is not correct. All the above says is that everything is passed as
a list. While the list is flat, it actually contains references to the
elements of the list.
For example:
sub f { $_[0] = 1; }
my $i = 0;
&f($i);
print("$i\n");
prints 1<new-line>.
You can avoid pass the effects of by reference by changing the
subroutine to work with copies:
sub f { my ($n) = @_; $n = 1; }
> In other words, yes, it is safe to just say "foo($dbh)" , but don't start
> thinking that everytime you pass an argument to a subroutine that you are
> passing a reference, because you are not unless you explicitly do so.
Passing arguments explicitly by reference is only useful is you want to
pass an array or hash as a single entity.
dd
--
David Dooling
