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From: Richard Stallman <rms@gnu.org>
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Subject: Re: Emacs Lisp and Guile
Date: Tue, 30 Jul 2002 23:54:54 -0600 (MDT)
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    > Scheme variables are normally lexical.  What do people normally do in
    > Scheme when you want a dynamically scoped value?

    In plain Scheme, you use 'dynamic-wind' to establish a dynamic
    context.  Entering and leaving that context will run specified
    procedures that can swap values in and out of variables that should
    have dynamically scoped values.

It is very undesirable for Lisp dynamic variables to be different
from Scheme dynamic variables.  It makes the system specs incoherent.

Is it possible to extend dynamic-wind so that it can handle
buffer-local, frame-local, etc. contexts?  Then a Lisp variable
could be handled with dynamic-wind as usual, and there would be
no divergence between Scheme variables and Lisp variables.

    In Guile, we also have 'fluids'.  A fluid is a normal object like a
    cons pair that holds one object per thread.  That is, fluids are our
    mechanism for thread local variables.

Could this be unified with dynamic-wind also?