Ed wrote:
> Any ideas on how to handle this with the 'is' keyword? I was
> reading the slashdot comments to Exegesis II, and this seemed to be
> the one issue that had merit. A couple of the posters bemoaned the
> fact that they were debugging PL/I about 25 years ago, and had code
> that depended on some obscure property being set somewhere earlier,
> which affected the code 1200 lines later.
>
> I could see that being a problem:
>
> undef $fh;
>
> $fh is true;
>
> ... 1200 lines later...
>
> if ($fh) { print "HERE!!!\n"; }
>
> In other words, 'is' seems to me to be a generous helping of
> action at a distance.
I don't see that at all. We're simply providing one more
way for a value to be true, and one more way for it to be false.
You might as well argue that the following is "action-at-a-distance":
undef $fh;
$fh = "0 but true";
... 1200 lines later...
if ($fh) { print "HERE!!!\n"; }
It's probably just a matter of coding what you actually mean. In Perl 5
and 6 your version means "if $fh is true in *any* possible way...",
whereas you seem to want "if $fh is defined", which is:
if (defined $fh) { print "HERE!!!\n"; }
in both Perl 5 and Perl 6.
> Is dumper going to become a built in keyword to handle this sort
> of thing?
Huh? I don't see the connection.
> Also, what's the difference between a 'property' and an
> 'attribute', ie, are:
>
> $fh is true;
>
> and
>
> $fh.true(1);
>
> synonyms?
No. The former means:
"Set the true property to 1 and return an alias to $fh"
The latter means:
"Attempt to call the C<true> method of $fh. If there is no such
method, set the true property to 1 and return that value"
> Can 'undef' valued thingys have properties
Yes.
> and functions?
No.
> And are the traditional data elements of a scalar (like value)
> simply attributes of a universal scalar object?
No.
Though the operations on a scalar might well be methods of the SCALAR class.
> And if all of the above is true, what does this do to the size of
> the internal representation of a scalar?
In the worst case, it adds a single pointer to it. But it's entirely
possible that properties would be stored centrally, in which case
there's no impact at all.
Damian
