RE: Properties and "0 but true".

[Austin Hastings]

> That's not how I see it.  The filehandle is naturally true if
> it succeeds.  It's the undef value that wants to have more
> information. In fact, you could view $! as a poor-man's
> way of extracting the error that was attached to the last
> undef.

Hmm. Thus?

sub fuu()
{
   my $retval is error("Unknown error") = open("file.ext");
   $retval is error($!) unless $retval;
   return $retval;
}

sub bahr()
{
   my $result = fuu();   # $results gets properties from $foo::retval

   if ($result) { blah(); }
   else { print $result.error(), "\n"; }
}

Now, what about magic properties? If we have const, volatile,
memoizable, etc, what are the rules for when those get replaced?

my $PI is constant = 3;
my $new_pi = $PI;       # Is $NEW_PI constant?
my $C = $PI * $RADIUS * 2; # Is $C constant?
                           # Would $C be constant if $RADIUS was?

sub pi() is memoizable { return $PI; }

Can I say <<'THIS',
my $subref is memoizable = \&pi;
THIS

and declare a ref to memoizable subs? Will the compiler warn on this
basis? Or will the subs only be memoizable if called via subref?

And why can't I dynamically declare function properties? If I'm writing
a reporting application, and I successfully get an exclusive lock on
the db, then let me improve the performance of my application.

=Austin


   

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