> Simplifying somewhat (ok, a heck of a lot), an rvalued:
>
> $foo is bar
>
> or
>
> $foo : bar
>
> is syntactic sugar for:
>
> bar($foo)
>
> with some extra magic for handling a properties hash
> associated with $foo's value, in particular resetting the
> hash when $foo's value changes.
>
> Right?
No. I do not think $foo will be passed to the bar handler like that.
> Basically, perl will (do the equivalent of) define a sub bar
> if it doesn't exist, then call bar, and bar can attach some
> data to the value in $foo, or update some data attached
> to the value in $foo, and will always return $foo.
>
> Right?
Yes.
> If I got the above badly wrong, the rest of this post
> probably won't make sense.
>
> I also presume it would make sense to alias $_ to $foo
> in (the method associated with) bar. (Is that intended?)
There will need to be some way to access the referent that the
property handler is invoked upon. Passing a reference
to it in $_ might be one such way.
> One could generalize so that bar can do as above, but
> doesn't _have_ to do as above, ie it doesn't have to
> attach data to $foo's value or update that data;
Yes. For example, it might just write out a log message
(indicating that $foo has been declared) or it might set
some other variable indicating that $foo has been bar'red.
> it can return a value other than $foo;
I would not expect that this would be allowed.
> and it can change the value of $foo.
Yes. For example:
my $foo is persistent;
> Basically, an rvalued:
>
> $foo : bar
>
> becomes a syntactically and cognitively cheap way, and
> a cognitively very different way, of calling bar on $foo, a
> cheapness and difference that amplifies if one applies
> several of these:
>
> $foo : bar baz qux
>
> instead of
>
> qux(baz(bar($foo)))
Err. No. That would be:
bar(1); baz(1); qux(1);
or possibly:
$_=\$foo; bar(1); baz(1); qux(1);
> I realize this isn't particularly appealing, but bare with me
;-)
> a little longer.
>
> So, in:
>
> $foo : bar
>
> bar in this context is not a property, but instead a more
> general "post" or similar (alluding to the notion that it is
> a bit like a postfix sub as well as (possibly) having the
> sticky note aspect.)
No. There will, I hope, be a mechanism for pre- and postfixing
subroutines, but not properties I think.
> So, to recap:
>
> $foo : bar;
>
> means bar is posted to $foo. $foo's value may change
> or stay the same. The return value may be $foo's, either
> before or after posting, or some other value. $foo's value
> may now have an attached bar postit.
You lost me here. Your ideas for properties are different from mine
(which may well, in turn, be different from Larry's).
Damian
