SPUG: Introspective parameters... Can a parameter know it's argument's name from the caller's perspective?

[Michael R. Wolf]

Wow!  This looks like the work of a devil (BTW, how long have you known that
MENGARINI summed as ASCII is 666?).

This is the ugliness I was trying to avoid.  Thanks.  And not.

"Thanks" because *I* don't have to apply brute force and awkwardness to get
my solution.

"Not" because it shows me that the only solution *is* brute force and
awkwardness.

But (to love the ugly !$#%$%) it's at least cool that Perl lets us do this
kind of thing.

I agree with the imbedded rant...

Thanks ** N,
Michael

-- 
Michael R. Wolf
    All mammals learn by playing!
        MichaelRWolf at att.net

> -----Original Message-----
> From: Will Mengarini [mailto:seldon at eskimo.com]
> Sent: Saturday, June 28, 2008 4:55 AM
> To: Michael R. Wolf
> Cc: spug-list at pm.org
> Subject: Re: SPUG: Introspective parameters... Can a parameter know it's
> argument's name from the caller's perspective?
> 
> * Michael R. Wolf <MichaelRWolf at att.net> [2008-06-27 17:22]:
> > [...] I'd like to do something like this: [...]
> > foreach $variable ($first_name, $last_name, $favorite_language) {
> >    debug_blather($variable);
> > }
> >
> > And get output like this...
> >
> > $first_name			(in namespace 'main::') has a value of
> > 'Michael'
> > [...]
> 
> Here's how I do it.  First I'll show the
> result, then the code that implements it.
> 
> I can code
>   eval show qw/$options{c} @foo/ if dbg;
> in a script, and get a display of the values of $options{c} and @foo,
> each identified by name, if C<dbg> returns true (which depends on whether
> there's a -D in the script's invocation).  Another example:
>   eval show if dbg 2;
> displays $_ if -DD was on the command line.
> 
> Eval is used so lexicals work.
> 
> Here's the code, brutally ripped from an ancient script.
> I haven't done any retesting to be sure it still works.
> I think this was developed for Perl 5.6.1.
> 
> use Dumpvalue;
> sub show (@) { # e.g. C<eval show '$n @n'>; need eval to access lexicals
>   # <rant>Even *FORTRAN IV* had this capability (called it
> NAMELIST)!</rant>
>   my $line = (caller)[2];
>   my $items = '';
>   for my $item( split(' ', @_ ? join(' ', at _) : '$_') ){
>     my $funnyChar = substr $item, 0, 1;
>     if( $funnyChar eq '$' ){
>       $items .= <<"      code";
>         print 'line $line $item: ';
>         \$show__Object->dumpValue($item);
>       code
>     }elsif( $funnyChar eq '@' || $funnyChar eq '%' ){
>       $items .= <<"      code";
>         print 'line $line $item:',\"\\n\";
>         \$show__Object->dumpValue(\\$item);
>       code
>     }elsif( $funnyChar =~ /[~!^&-+=\\|\/]/ ){ # construe as expression
>       $items .= <<"      code";
>         print 'line $line $item: ',$item,\"\\n\";
>       code
>     }else{
>       $items .= <<"      code";
>         print 'line $line $item',\"\\n\";
>       code
>     }
>   }
>   chop $items;
>   return <<"  code";
>     select((
>       select(STDERR),
>       do {
>         my \$show__Object = new Dumpvalue or die;
>         local \$\\;\n$items
>       }
>     )[0]);
>   code
> }
> 
> sub dbg (;$) { # E.g "foo if dbg; bar if dbg 2" means foo if -D, both if -
> DD
>   defined $main::op{D} && $main::op{D} >= ($_[0] || 1)
> }
> 
> --
>                  Will Mengarini  <seldon at eskimo.com>
>          Free software: the Source will be with you, always.
>          perl -le "print eval join '+',unpack 'C*',MENGARINI"