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Re: PCL Bombing on dynamic slots
- To: mbm@caf.MIT.EDU
- Subject: Re: PCL Bombing on dynamic slots
- From: Gregor.pa@Xerox.COM
- Date: 29 Mar 87 18:35 PST
- Cc: Gregor.pa@Xerox.COM, wallace@ucbarpa.Berkeley.EDU, commonloops.pa@Xerox.COM
- In-reply-to: mbm@caf.MIT.EDU (Mike McIlrath)'s message of Sat, 28 Mar 87 09:27:04 EST
I should have put a more careful explanation of the demise of :dynamic
slots in my previous message.
After looking at :dynamic slots carefully, we decided that in almost all
cases, they did not give an advantageous space/performance tradeoff.
just providing :dynamic slots as an option means that every instance
of every class with meta-class class, is one word bigger. Regardless of
whether the class uses :dynamic slots.
for instances which do have :dynamic slots, it takes 4 words of
storage to store the value of the slot rather than the 1 word it takes
if the slot is a :instance slot.
When you add this up :dynamic slots just don't seem worth it, most
programs which did use them will do just as well or better to use
:instance (the default) slots.
Of course, for a program which reall does want something like :dynamic
slots, its pretty easy to do using the meta-object protocol.