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On Thu, Nov 11, 2004 at 04:05:50PM -0500, Aaron Brown wrote:

> > Aaron, Guile's set! syntactic keyword is not legal
> > Scheme.  :-)
> Is any type of reassignment legal Scheme?

I don't actually know, new keywords turned up (until Y2K at least)
with remarkable frequency.  But set! was the one that caused friction
between the imperative and lambda calculus people.  There were a lot
of compromise proposals on the table, like closure implementations
that created environments that set! couldn't touch.

That was the sticking point:  breaking closures, since pure functions
(as created by closure) have to be referentially transparent for all
their good mathematical properties to apply.  Needless to say, if the
closed environment of a closure is modified, referential transparency
disappears completely.

Rich Artym.
Existing media are so disconnected from reality that our policy debates
spin around a fantasy world in which the future looks far too much like
the past.