Re: Proposal for EVAL

[Adri en Hans Durieux <xerox@cs.vu.nl>]

In your letter dated Wed, 20 May 92 10:22:33 EDT, Mark Feeley wrote:

>It seems to me that Jinx's proposal DOES contain the notion of "first-class"
>environments.  The procedures NULL-ENVIRONMENT, INTERACTION-ENVIRONMENT,
>and SCHEME-REPORT-ENVIRONMENT return a value that can be used like any
>other value.  Granted, the proposal only specifies 3 possible environments
>and no specific operations on environments other than EVAL.  A better
>wording would probably be: "weak" first-class environments.  Anyway, this
>is just a detail.

I may be wrong, but if the result of (INTERACTION-ENVIRONMENT)
can be taken to another environment and still mean the environment
where (INTERACTION-ENVIRONMENT) was evaluated (this was not clear to me in
the original proposal, which I have unfortunately lost),
there is surely nothing "weak" about these environments?
Of course, it is always possible to add power (e.g. ADD-BINDING! might add
a binding, not by creating a sub-environment but by extending the current
one), but they seem quite powerful as they are.

If I remember well, INTERACTION-ENVIRONMENT wasn't supposed to be essential,
I suppose for this reason.

                                                          Biep.

P.S.: If INTERACTION-ENVIRONMENT didn't mean to mean the current
      environment I have misremembered.  It that case I beg your pardon.