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Constant: string NULL_KEY = "00000000-0000-0000-0000-000000000000";

The string constant NULL_KEY has the value "00000000-0000-0000-0000-000000000000"

NULL_KEY is a string. However it is only really useful as a key.

Despite fitting the syntax criteria to be a valid key, when fed to a Conditional as a key it executes as FALSE.

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•  attach


integer isKey(key in) {
    if(in) return 2;
    return (in == NULL_KEY);
}//returns 2 if it's a valid key, 1 if it's NULL_KEY
// NULL_KEY itself is evaluated as FALSE only when it is casted as a key.
default {
    state_entry() {
        if (NULL_KEY) { llOwnerSay("NULL_KEY is TRUE");  }// Correct.
        else          { llOwnerSay("NULL_KEY is FALSE"); }// Never.
        if ((key) NULL_KEY) { llOwnerSay("Casted NULL_KEY is TRUE");  }// Never.
        else                { llOwnerSay("Casted NULL_KEY is FALSE"); }// Correct.


Like any LSO string constants longer then 3 characters and used in multiple places in the code, they should be stored in a global variable. The result will be a considerable memory savings. This does not apply to scripts compiled with Mono. See LSL Constants vs Globals for more information about this and examples.
In most situations NULL_KEY isn't needed; an empty string ("") will suffice. To take advantage of this certain practices have to be avoided. In many applications keys are checked against NULL_KEY to determine if they are valid; this is bad practice.

LSL makes it easy to check if a key is valid. Simply use the key as the parameter for a conditional.

That is, instead of if(uuid != NULL_KEY), use if(uuid). if(uuid) will only return TRUE if it is a valid key that is also not a null key.

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   NULL_KEY is no longer a NULL_KEY when passed to a function


string NULL_KEY = "00000000-0000-0000-0000-000000000000";


My hopes for nothing
but for thirty two zeros,
have been dashed, four times.