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Date: Thu, 30 Sep 93 17:07:05 -0400
From: Michael R. Blair <email@example.com>
Is this an oversight or is there some subtle rationale behind the following:
literals are constants and therefore immutable.
other constructed composite data are mutable.
There is/are no predicate(s) to test mutability.
I think (tell me if I'm wrong) that constants are immutable to allow
sharing of constants. Predicates to decide mutability would require
to maintain run-time information about mutability -- which could be
expensive in some implementations.
Also, some systems use Scheme itself to compile the Scheme code. Those
systems would need to be augmented by procedures like
(immutable-cons <obj1> <obj2>)
etc. (The ``constants'' of the user program are not ``constant'' in