Re: current-environment

[Mikael Djurfeldt]

Aaron VanDevender <address@hidden> writes:

> I just posted to guile-sources a patch which defines a
> current-environment primitive. It allows you to hang on to an
> environment and then eval things in that environment later. So
> you can say stuff like this:
>
> (define env (let ((mesg "hello")) (current-environment)))
>
> (eval '(display mesg) env) 
>
> => "hello"
>
> I debated for a long time whether this environment should also
> carry the module context with it. i.e. should eval set the
> current-module to the module that was current when
> current-environment was called. I decided that it probably
> shouldn't since the module doesn't get pulled in when you close
> over an environment using lambda. Although I can sort of see the
> other side since the current use of eval *only* sets the current
> module. Anyway, I'd be interested to hear any discussion on this
> issue or this feature in general.

Including my reply on the guile-sources list (where I maybe shouldn't
have replied, since that list is for source only):

> --- Begin Message ---
>
>
>
> Subject: 
>
> Re: current-environment
>
>
>
>
> Date: 
>
> Sat, 15 Mar 2003 10:23:47 +0100
>
>
>
>
> User-agent: 
>
> Gnus/5.090015 (Oort Gnus v0.15) Emacs/21.2
>
>
>
>
> Aaron VanDevender <address@hidden> writes:
>
> > Here is a patch which adds the ability to obtain an environment
> > and eval using it.
>
> Thank you for your patch!  It is always nice to see people do
> intelligent things with the Guile source.
>
> But in this particular case: Doesn't this do the same thing as the
> combination of
>
>   (the-environment)
>
> and
>
>   (local-eval EXP ENV)
>
> ?
>
> I should add that there has been a lot of controversy about these two,
> since some people believe it would be an advantage for future
> compilers not to have to support this form of evaluation.
>
> Best regards,
> Mikael D.
>
> --- End Message ---