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Issue CONSTANT-MODIFICATION, version 2
- To: jeff%aiai.edinburgh.ac.uk@NSS.Cs.Ucl.AC.UK
- Subject: Issue CONSTANT-MODIFICATION, version 2
- From: Jon L White <firstname.lastname@example.org>
- Date: Tue, 10 Jan 89 00:52:23 PST
- Cc: email@example.com
- In-reply-to: Jeff Dalton's message of Tue, 10 Jan 89 00:39:18 GMT <firstname.lastname@example.org>
re: But why can't constants be modified in compiled code? It seems clear
that they could be, so there must be some reasons why they aren't
always modifiable, and those are the real reasons.
There's the implementational reason, as verified by the "current practice"
of several widespread implementations (I see Sandra invoked this reason
in her reply). There's also a semantic consistency reason -- "constants"
should be constant, and not simply global parameters subject to casual
alteration during the running of the program. Remember the "Indiana rule"
(setn pi 3.0)
-- JonL --
P.S., No typo! -- Interlisp has the SETN operator even though CL doesn't