[R6RS] Re: Zapping SET-CAR! & SET-CDR!
Wed Oct 20 13:07:42 EDT 2004
From: Michael Sperber <sperber at informatik.uni-tuebingen.de>
Date: Wed, 20 Oct 2004 16:51:35 +0200
RK> I am sympathetic
RK> to wanting immutable pairs, but I think it is too big change. Too many
RK> programs would break.
[...] I would be much less favorably inclined towards this change if
a majority at the Scheme workshop hadn't expressed they approved it.
I am surprised by this. How big a majority? 11 out of 20 is a
majority, 19 out of 20 is a mandate.
So, would an alternative be to make mutability more explicit in the
standard? Either by having something like MAKE-IMMUTABLE!, which
works on any kind of non-closure heap object, or by having
IMMUTABLE-CONS and so on. Then we could have argument lists be
immutable and at least reap some of the benefits.
I would be a lot happier with having both mutable and immutable
pairs, although it leaves open the question of which kind of pair
MAP, APPEND, and other procedures create. Having both might be
a problem for some implementations.
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