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 Ctrue 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
