[r6rs-discuss] set-car!

[Carl Eastlund]

On 6/22/07, Onnie Winebarger <owinebar at gmail.com> wrote:
>     Is this the only way to achieve that goal, or just a convenient one?
>     It is an unfortunate decision, in any case.  The Scheme that makes
> impurity second-class is not the true Scheme.

In this setup, it's easy to achieve a guarantee of purity (don't
import set-c[ad]r!), and easy to achieve impurity (import them).  It's
a one-line difference.  In previous Schemes, impurity is the default
but achieving purity requires examining the whole program, and there
was no builtin mechanism to guarantee it.  I think the R6RS solution
comes closer to making both kinds of programming first-class.

-- 
Carl Eastlund