[plt-scheme] Native code generation and immutable pairs

From: Lauri Alanko (la at iki.fi)
Date: Fri Mar 10 07:03:09 EST 2006

On Fri, Mar 10, 2006 at 01:22:29AM -0800, Noel Welsh wrote:
> There is always a tradeoff between changes that improve a
> language and supporting backwards compatability.  This is
> one of those cases.

So you are suggesting changing "cons"? What exactly would this buy? Any
new code can use immutable-cons, and any existing code can be easily
changed to use immutable-cons. Changing "cons" directly would only
benefit pure legacy code that would perhaps become automatically more
efficient without having to touch the code.

A change that only makes legacy code more efficient doesn't sound very
forward-thinking to me.

I do agree that immutability should be better supported and easier to
use than it currently is, but that doesn't require
backwards-incompatible changes.

What's so horrible about mutable cons cells, anyway? They are just
two-element structures. Do you want to make structures immutable as


Posted on the users mailing list.