Re: Vectors as functions

[Michael Vanier <address@hidden>]

<devil's advocate>
That makes sense, but I assume that the loss of optimization capability is
only for procedures that actually add new bindings at runtime, right?
Given that this is probably a fairly rare thing to want to do, what's the
big deal?  It's just a costly operation that you can choose to do or not to
do (like using continuations <duck>).  That doesn't mean it shouldn't be
available.
</devil's advocate>

What do you mean by syntactic binding in first-class environments?  Do you
mean defining macros in first-class environments?  Yes, I can see that that
would get pretty darned messy.

Mike


> From: "Joe Marshall" <jrm@ccs.neu.edu>
> Date: Fri, 15 Aug 2003 15:29:30 -0400
> 
> The biggest problem with first-class environments ala MIT Scheme
> is the introduction of new bindings at runtime.  If you introduce a
> new binding, the `lexical address' (frame and offset) of a variable
> cannot be statically determined and you have to do a deep search
> every time.  It absolutely destroys any sort of compiler optimization.
> 
> If you went a tad further and allowed *syntactic* binding in
> first-class environments, you'd be truly hosed.
> 
> 
> ----- Original Message ----- 
> From: "Michael Vanier" <mvanier@cs.caltech.edu>
> To: <brlewis@alum.mit.edu>
> Cc: <sperber@informatik.uni-tuebingen.de>; <ll1-discuss@ai.mit.edu>
> Sent: Friday, August 15, 2003 14:30
> Subject: Re: Vectors as functions
> 
> 
> >
> > > From: Bruce Lewis <brlewis@alum.mit.edu>
> > > Date: 15 Aug 2003 14:10:11 -0400
> > >
> > > Michael Vanier <mvanier@cs.caltech.edu> writes:
> > >
> > > > I'm thinking of situations where you might have a list of symbols
> > > > representing names (or first-class names) and you might want to set
> their
> > > > values to a given value, like mapping set! over the list of names.
> Not
> > > > having names as first-class entities makes that unduly hard.
> > >
> > > If you're sure you want to do it this way, and not use a hash table to
> > > deal with names at run time, then you probably want Common Lisp.
> > >
> >
> > How would you use a hash table to deal with names at run time?
> >
> > [To Mike Sperber] Does "set" in common lisp destroy lexical scoping?  I'm
> > not sure exactly what you were getting at, although I dimly understand
> that
> > there could be a problem.
> >
> > I feel like first-class environments a la MIT scheme are also relevant to
> > this discussion, but I don't really know much about them.  Any MIT
> schemers
> > want to comment?
> >
> > I guess the bottom line is: how much freedom to mess around with the local
> > environment is consistent with lexical scoping?
> >
> > Mike
> >
>