On Sun, 5 Jan 2003, Murat Ünalan wrote:
> > Properties *can* be smart-matched:
> >
> > print "creditcard" if $var.prop().{CreditCard} ~~ 'VISA';
> > or:
> > print "creditcard" if $var.prop{CreditCard} ~~ 'VISA';
> > or:
> > print "creditcard" if $var.CreditCard ~~ 'VISA';
> >
> I think this is similar to "John Williams" suggestion:
>
> print "creditcard" if CreditCard( $var ) eq 'VISA';
Well, no. In my suggestion, CreditCard is a sub which checks whether $var
is a valid credit card, returning the card type.
In Damian's example, he is assuming $var already has a property assigned
to it called CreditCard possibly containing the value 'VISA'. So his has
less processing they either of ours.
The problem I see with:
> print "creditcard" if $var ~~ CreditCard( 'VISA' );
is that CreditCard does not know what $var is. Even if you overload the
smartmatch operator on $var's class, it is still comparing $var with the
value returned from CreditCard.
> sub CreditCard
> {
> #connect to a "specific" database (VISA, MASTERCARD, ..)
> #compare with "non-blocked or valid" cards
> }
...
> Excerpt: My concept is to have a twofold view about "properties". One
> thing that is attributing a type during decleration, and something that
> could verified against in other context. All my thinking on that
> orginates from Damians Attribute::Type.
>
> Hopefully i do not confuse you too much.
A sub is not a property. It might be a method, which could sometimes look
like a property (as in Damian's third example), but you have strayed so
far away from properties that you are talking about something else now.
~ John Williams
