Re: vm branch now uses vm repl by default

[Andy Wingo <wingo@pobox.com>]

On Tue 09 Sep 2008 10:41, ludo@gnu.org (Ludovic Courtès) writes:

> So, previously, there was `variable-ref':

There still is. It is used when a variable is bound immediately, when it
is pushed on the stack by a link-now instruction.

    scheme@(guile-user)> ,c (define x a)
    Disassembly of #<objcode b7feb6d0>:

    nlocs = 0  nexts = 0

       0    (load-symbol "a")               ;; a
       3    (link-now)
       4    (variable-ref)
       5    (define "x")
       8    (variable-set)
       9    (void)
      10    (return)

> Now, there's also a vector associated with each closure to store
> references to global variables, right?  Looks better!

That's always been the case IIRC, only before it used to push and pop a
bit more -- instead of

    (late-variable-ref 0) 

it would be

    (object-ref 0)
    (variable-ref)

where the object was instantiated by a load-symbol / link-now pair. But
that's not how Guile's toplevel lookups occur, so I added the new
behavior, which has the added benefit of not pushing and popping so
much.

> (Hint: the doc is outdated.  :-))

It's still correct, just not complete :-) I'll get on it at some point,
probably folding into Guile's docs somehow.

>>     scheme@(guile-user)> ,option interp #t
>
> That means good old `CEVAL ()' is used, right?

Yep, whatever (language-evaluator (repl-language repl)) does -- which
for `scheme' is `eval'.

    http://git.savannah.gnu.org/gitweb/?p=guile.git;a=commitdiff;h=02ed0d3df2607c5d78fbc38cbb82a65df1bc7080

> When that is the case, one can still use `{eval,debug}-options', right?

Yep

> It'd be nice if we could find a way to "do something" with the
> `current-reader' fluid at compilation time, like detecting top-level
> `(fluid-set! current-reader ...)' statements and use that to switch the
> compiler's reader (hacky...).

Perhaps, there is already a repl-reader fluid for readline's benefit.
Note also that languages have readers as well, so that e.g. elisp can
read differently from scheme.

Andy
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