Static Scoping versus Dynamic Scoping

Static Scoping versus Dynamic Scoping

[Davin Pearson]

I read somewhere that in the future dynamic scoping of variables
in
Emacs Lisp will be replaced with static
scoping.

I don't want this to happen because I often need to make use of
the
following
idiom:

(let ((case-fold-search
t))
 
(foo))

Inside the foo function case-fold-search's value is set to t,
whatever
the global value for case-fold-
search.

Could someone please reassure me that this precious feature will
not
be removed?

Re: Static Scoping versus Dynamic Scoping

[David Kastrup]

Davin Pearson <davin.pearson@gmail.com> writes:

> I read somewhere that in the future dynamic scoping of variables in
> Emacs Lisp will be replaced with static scoping.
>
> I don't want this to happen because I often need to make use of the
> following idiom:
>
> (let ((case-fold-search
> t))
>  
> (foo))
>
> Inside the foo function case-fold-search's value is set to t,
> whatever the global value for case-fold- search.
>
> Could someone please reassure me that this precious feature will not
> be removed?

Variables defined with defvar will not be affected by the change.
There is no work in progress that would make this change likely in the
next 7 years, anyway.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum

Re: Static Scoping versus Dynamic Scoping

[Stefan Monnier]

> I read somewhere that in the future dynamic scoping of variables in Emacs
> Lisp will be replaced with static scoping.

You're confused.  There is some work going on which attempts to *add*
static scoping (more seriously than provided by CL's lexical-let macro).
But there's no intention to drop dynamic scoping: it would break about 99%
of existing Lisp code.


        Stefan

Re: Static Scoping versus Dynamic Scoping

[Tom Tromey]

>>>>> "Stefan" == Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> I read somewhere that in the future dynamic scoping of variables in Emacs
>> Lisp will be replaced with static scoping.

Stefan> You're confused.  There is some work going on which attempts
Stefan> to *add* static scoping (more seriously than provided by CL's
Stefan> lexical-let macro).  But there's no intention to drop dynamic
Stefan> scoping: it would break about 99% of existing Lisp code.

I'm curious about this.  I know about the branch for this but I
haven't seen any discussion about merging it to the main line...

Tom

Re: Static Scoping versus Dynamic Scoping

[Stefan Monnier]

> I'm curious about this.  I know about the branch for this but I
> haven't seen any discussion about merging it to the main line...

There was a long discussion about it before the branch was created,
i.e. many years ago.  IIRC Richard was not highly interested but might not
oppose it as long as it didn't make the current code more complex and
ensured 100% backward compatibility.

Since then Miles has done a good bit of the work, but I don't know exactly
what's missing.  I know the trickier part is writing the byte-compiler.
IIRC the interpreter has been working reliably for a while now.


        Stefan