[plt-scheme] Native code generation and immutable pairs

On 2/11/06, Robby Findler <robby at cs.uchicago.edu> wrote:
> At Fri, 10 Feb 2006 00:07:55 -0800, Jim Blandy wrote:
> > If MzScheme is heading down the native code generation route, have you
> > thought much about making pairs immutable?
>
> I don't know if anyone answered your question, but yes. We are
> considering that and have been for a long time. Partly because it
> improves analyses like you suggest, but more because it makes it easier
> to reason about programs using immutable conses (and contract systems
> work better when structures are immutable). In particular, you can hand
> out the same list multiple times from a library without having to worry
> about copying it to be safe/correct.

I see on http://www.cs.indiana.edu/~dyb/r6rs/status.html that the R6RS
committee has reaffirmed that set-car! and set-cdr! will be in the
language.  So let me push further: have you folks made a decision on
this yet?