[Omaha.pm] Class::Date - change once set

[Jay Hannah]

On Nov 11, 2005, at 3:06 AM, Balázs Szabó (dLux) wrote:
>>>    $x = $_[0];
>>
>> $x is created, a new obj in year 2000.  (via clone() inside 
>> Class::Date)
>
> Not correct.  $_[0] is always points to the same object as $a, $_[1]
> always points to the same object as $b; In this case, we have a new
> object, $x, which is also points to the same as $a and $_[0];

Oh. At a glance inside the guts of your class and not knowing 
"overload" well I thought Class::Date was doing operator overloading on 
the assignment operator (=), invoking clone().

Now I've read up a little (perldoc overload) and may understand your 
guts better. Your explanation above explains that the assigment above 
is a vanilla Perl reference assignment, not some deep overloaded 
magic...

This part of "perldoc overload" wigs me out:

> SPECIAL SYMBOLS FOR "use overload"
>
> ...
>
>        Copy Constructor
>
>        The value for "=" is a reference to a function with three 
> arguments,
>        i.e., it looks like the other values in "use overload". 
> However, it
>        does not overload the Perl assignment operator. This would go 
> against
>        Camel hair.

"would go against camel hair?" lol! Jay swoons w/ bemused 
incomprehension. I thought NOTHING was sacred inside overload. -laugh-

Debugging your class objects always trips me up because of your (very 
useful)

> use overload
>   '""'     => "string",

I'm used to debugging and seeing this:

   DB<1> p $x
main=HASH(0x8d3a28)

But on your objects I get this:

   DB<2> p $a
2000-11-11 00:00:00

So when I'm trying to understand what happens during/after an 
assignment operation I fail. -grin-  Now that I know there's no magic 
going on I can understand it, but I won't know for sure when I'm 
looking at it in the debugger.

Is there any way to get the "main=HASH(0x8d3a28)" to kick out on your 
objects? (So I can SEEE if its the same obj or some new one?)

> So, it does not copy OBJECTS, it just increasing and decreasing
> reference counters to objects (since perl is a reference-counting 
> language).
>
> Please see the perlobj and perlref (or perlreftut) manual to get what I
> had talked about.

Yes. I understand that default behavior. I thought Class::Date was 
being sneakier than the default.

Thanks again for the help, you mad scientist genius you,  -grin-

j