Paul Berkowitz wrote:
>>Anyway, the thing to remember is that AppleScript's record type is comparable to C structs [...] AS records and C structs are used to define complex rigid data structures at compile-time
>
>That is not true at all. First of all, AppleScript records are not
>immutable: you can change the value of any key.
I never said records were immutable. I said their structure was. You misread.
>Secondly, NSDictionary is precisely a "rigid" immutable data structure [...]
>NSMutableDictionary which is dynamic: perhaps that's what you meant to say.
Oops, yes. Meant NSMutableDictionary (though not for the reasons you think).
>record is a native dictionary type:
It is NOT a dictionary type. Let me see if I can provide a better definition as that first one wasn't so great:
- A dictionary is a collection of key-value pairs where both the keys and values are objects. To retrieve a value from a dict, you pass it an object which it uses as a key to look up the corresponding value. Mutability [1] is a red-herring, btw; what's signficant is how the data is stored.
- An AppleScript record is collection of properties defined at compile-time (comparable to a C struct or a class instance containing only public instance variables). Only the values are objects; the properties they're stored in are part of the record's structure, not its content. To retrieve a value from a record, you refer to the property that contains it using the appropriate identifier.
Hope that clarifies,
has
[1] With immutable dicts, key-value pairs are added when the object is created; in mutable dicts, they can be added, removed and replaced at any time. The data is stored and retrieved exactly the same way though.
--
http://freespace.virgin.net/hamish.sanderson/
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