[plt-scheme] Native code generation and immutable pairs

From: Noel Welsh (noelwelsh at yahoo.com)
Date: Fri Mar 10 04:22:29 EST 2006

--- Lauri Alanko <la at iki.fi> wrote:

> So what exactly are you proposing? cons-immutable is
> available already for anyone wanting to use it. Making
> procedure named "cons" produce
> immutable pairs by default would break half the world and
> then some.

There is always a tradeoff between changes that improve a
language and supporting backwards compatability.  This is
one of those cases.   More immutability makes concurrency
easier, and our best guess of the what the computing world
of the next 5 years will look like includes a great deal of
multicore chips.

My opinion is that (PLT) Scheme should make these decisions
in favour of improving the language.  If I want a language
that isn't cutting edge, there are plenty already. 
However, I see R6RS as a 'catch-up' spec.  It's been so
long since R5RS that it is essentially just bringing the
spec up to date with current implementations.  I expect
R7RS to be more aggressive.  For example, I'd like to see
multiple values and mutable cons cells out the door though
obviously others feel differently -- don't bother emailing
me to tell me this!  The degree of compatability that PLT
should maintain with standard Scheme is another issue, that
I also don't particularly want to get into.


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