On 8/16/06, David Green wrote:
   $a=[1, 2, [EMAIL PROTECTED];
   $c=[1, 2, [EMAIL PROTECTED];
   $d=[1, 2, [EMAIL PROTECTED];

        $a =:= $c;      #false, different variables
        $a === $c;      #true, same elements make up $a and $c
        $a eqv $c;      #true, same elements therefore same values

        $a === $d;      #false, [EMAIL PROTECTED] and [EMAIL PROTECTED] are 
different refs

So $a, $c, and $d may all have the same *value* (or "snapshot", when evaluated all the way down through nesting and references), i.e. they might be eqv, but only $a and $c are === because they have the same contents [unevaluated contents] and $d doesn't.

OK, here's the counter-argument to my incessant ranting:

In the above example, $a and $c do "look" awfully similar, but suppose we replace the anonymous arrays with named ones:

        @X1=(1, 2, [EMAIL PROTECTED]);
        @X2=(1, 2, [EMAIL PROTECTED]);


Now $a clearly does NOT === $b, because @X1 and @X2 are different variables (that just coincidentally happen to share the same contents at the moment). Replacing @X1 and @X2 with their anonymous equivalents shouldn't suddenly change that.

[Well, anonymous object could have different rules, I suppose, but it's no longer "obvious" that they should. Strings, for example, do have special treatment to make different string-objects look the same, but strings can't contain other variables, so it's easy to make them act like plain values.]

However, it also follows that @X1 !=== @X2. There's no anonymous reference hiding there, so why aren't @X1 and @X2 the same? (Well, they just aren't!) So... probably what I wanted all along is just to compare the contents of an array -- and === just isn't it. Hm.

        =:= checks for same variable
        === checks for same object
        eqv checks for same value

except that if the operands aren't objects, === will compare them as values (like eqv). Or rather, if an item is a value (or an object that ought to act like a value), just make sure its SKID (which === uses) compares in an appropriate value-like way.


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