Re: Re: passing of values by reffernence and taint mode?

at this point it seems clear to me that i have no idea what i am doing.... after messing with this for the last hour the best i have gotten is

#!/usr/bin/perl -w
use strict;
my $thingy = "No Change\n";
print $thingy;

&change($thingy);

print $thingy;

sub change
{
  my $in = shift;
  $$in = "Changed\n";
}
[download]

I get the following error

Can't use string ("No Change") as a SCALAR ref while "strict refs" in 
+use at asdf.pl line 12
[download]

It seems like it is doing some sort of weird passing by value thing to me... but then I have no idea what I am doing (haven't you noticed...sigh) I read through perlref and it mentioned this problem existed but I could discern no answer also the 2 perl books I have on hand made similar statments with no answer I could find.

and I forgot to login, blast I guess today is not my day.......

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Re: Re: Re: passing of values by reffernence and taint mode? by djantzen (Priest) on Jun 06, 2003 at 17:19 UTC
It seems like it is doing some sort of weird passing by value thing to me Yes, but it's not weird, it's doing exactly what you're telling it -- passing a string that you're then trying to dereference. Look at hardburn's post and you'll see the critical difference is the backslash preceding the scalar. `&change($thingy); # passes by value &change(\$thingy); # creates and passes a reference` [download] "The dead do not recognize context" -- Kai, Lexx	[reply] [d/l]
Re: Re: Re: passing of values by reffernence and taint mode? by hardburn (Abbot) on Jun 06, 2003 at 17:22 UTC
First, you should avoid the ampersand syntax unless you have a specific reason to use it. Second, you're passing by value, not by referance. When you get to the `$$in = "Changed\n";` part, perl tries to use `$in` as a symbolic ref. Symbolic refs are (rightfully) illegal with strict 'refs' turned on, hence the error message. To pass by a hard referance, you need to change how you call the sub to `change(\$thingy);`. Notice the '\' before the '$', which is saying "make a referance to `$thingy`". No change should be necessary to the subroutine itself. ---- I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident. -- Schemer Note: All code is untested, unless otherwise stated	[reply] [d/l] [select]