[oak perl] Re: [sf-perl] print Dumper \$|;

[Paul Makepeace]

On Thu, Jan 16, 2003 at 09:26:24AM -0800, Belden Lyman wrote:
> Paul Makepeace wrote:
> >On Wed, Jan 15, 2003 at 04:30:44PM -0800, Belden Lyman wrote:
> >
> >>Flush pipes, print $|:
> >>
> >>   % perl -MData::Dumper -e '$|++; print Dumper \$|'
> >>   $VAR1 = \'1';
> >>
> >>Okay, I believe that.
> >>
> >>Clog pipes, print $|:
> >>
> >>   % perl -MData::Dumper -e '$|--; print Dumper \$|'
> >>   $VAR1 = \'1';
> >>
> >>Huh? Same value? That can't be right though, because
> >
> >
> >This is a known perl oddity, and often used by golfers and obfuscators
> >as a toggler.
> >
> >$ perl -le 'print "p",--$|,"ng!" for 1..4'
> >p1ng!
> >p0ng!
> >p1ng!
> >p0ng!
> >$
> >
> >Paul
> >
> 
> 
> Sure, I know that. :)
> 
> My intended question was, "How come Data::Dumper thinks $|-- has the
> same value as $|++ ?"

Because they *do* have the same value: --$| == ++$|

The use of Data::Dumper is a red herring here. You've accepted that $|
is magical but haven't shown in any way that DD is inconsistent with
simply printing its value.

> Your example is better at showing that $| obviously is changing value.
> But it doesn't explain why printing $| using Data::Dumper always gives
> back \'1', seemingly without regard to the actual value of $| at the
> time.

That's because you fiddled with it each time before you printed it :-)
To wit,
> >>   % perl -MData::Dumper -e '$|++; print Dumper \$|'
> >>   % perl -MData::Dumper -e '$|--; print Dumper \$|'

If you leave it unfettered it'll come back zero,

$ perl -MData::Dumper -e 'print Dumper \$|'  
$VAR1 = \'0';
$

I could've misunderstood the question a second time, in which case I'll
just keep quiet from now :-)

Cheers,
Paul

PS Next post has to covertly use someone else's last name in it...

-- 
Paul Makepeace ....................................... http://paulm.com/

"If the answer is 5, then evolution will determine the colour."
   -- http://paulm.com/toys/surrealism/