Change the default binding of C-x C-e ?

Change the default binding of C-x C-e ?

[Mike Mattie]

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Hello,

I think it is a good idea to change the default key-binding of C-x C-e to eval-defun. From a reading of the Elisp
Intro I became used to using the usual binding which is eval-last-sexp. Things worked fine until I progressed
in elisp to where I wanted to use defvar. As the informed have probably surmised I was baffled by the results
because repeated evaluation did not affect the default value.

While reading through the manuals I stumbled across eval-defun and realized what was going on. AFAICT they
are effectively the same in use, however eval-defun does not have suprising corner cases like defvar default
values.

FWIW it may help others to change this binding.

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Re: Change the default binding of C-x C-e ?

[Leo]

On 2008-01-06 11:41 +0000, Mike Mattie wrote:
> Hello,
>
> I think it is a good idea to change the default key-binding of C-x C-e to eval-defun. From a reading of the Elisp
> Intro I became used to using the usual binding which is eval-last-sexp. Things worked fine until I progressed
> in elisp to where I wanted to use defvar. As the informed have probably surmised I was baffled by the results
> because repeated evaluation did not affect the default value.
>
> While reading through the manuals I stumbled across eval-defun and realized what was going on. AFAICT they
> are effectively the same in use, however eval-defun does not have suprising corner cases like defvar default
> values.
>
> FWIW it may help others to change this binding.

Do you know about "C-M-x"?

-- 
.:  Leo  :.  [ sdl.web AT gmail.com ]  .:  [ GPG Key: 9283AA3F ]  :.

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Re: Change the default binding of C-x C-e ?

[Mike Mattie]

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On Sun, 06 Jan 2008 14:59:11 +0000
Leo <sdl.web@gmail.com> wrote:

> On 2008-01-06 11:41 +0000, Mike Mattie wrote:
> > Hello,
> >
> > I think it is a good idea to change the default key-binding of C-x
> > C-e to eval-defun. From a reading of the Elisp Intro I became used
> > to using the usual binding which is eval-last-sexp. Things worked
> > fine until I progressed in elisp to where I wanted to use defvar.
> > As the informed have probably surmised I was baffled by the results
> > because repeated evaluation did not affect the default value.
> >
> > While reading through the manuals I stumbled across eval-defun and
> > realized what was going on. AFAICT they are effectively the same in
> > use, however eval-defun does not have suprising corner cases like
> > defvar default values.
> >
> > FWIW it may help others to change this binding.
> 
> Do you know about "C-M-x"?
> 

I do now. I have eval-defun bound to a key-sequence that works for me. I addressed
the mailing list because I thought others might stumble as I did on this particular
issue while learning elisp.

A note in the Emacs Lisp Intro would likely only confuse the learning process at
the earliest stage which is precocious. I thought that using eval-defun from
the beginning would side-step trouble down the road with defvar altogether.

So the issue is resolved for me, my concern was for others travelling the
elisp path.

Cheers,
Mike Mattie

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Re: Change the default binding of C-x C-e ?

[Alan Mackenzie]

Hi, Mike!

On Sun, Jan 06, 2008 at 03:41:04AM -0800, Mike Mattie wrote:
> Hello,

> I think it is a good idea to change the default key-binding of C-x C-e
> to eval-defun. From a reading of the Elisp Intro I became used to using
> the usual binding which is eval-last-sexp. Things worked fine until I
> progressed in elisp to where I wanted to use defvar. As the informed
> have probably surmised I was baffled by the results because repeated
> evaluation did not affect the default value.

> While reading through the manuals I stumbled across eval-defun and
> realized what was going on. AFAICT they are effectively the same in
> use, however eval-defun does not have suprising corner cases like
> defvar default values.

eval-last-sexp and eval-defun do different things - e-d determines the
top level construct surrounding point, e-l-s finds the previous
expression.  I think you've just found that out.

It is sometimes useful whilst hacking lisp to evaluate an expression in
the middle of a defun.  You'd be surprised how often that happens.
That's what C-x C-e is for, and I'd bet my entire life savings on the
rest of the Emacs team agreeing here.

> FWIW it may help others to change this binding.

Maybe, maybe not.  I would suggest a compromise binding: C-u C-x C-e for
eval-defun.  You could implement that for yourself using "advice".

-- 
Alan Mackenzie (Nuremberg).

Re: Change the default binding of C-x C-e ?

[Stefan Monnier]

> It is sometimes useful whilst hacking lisp to evaluate an expression in
> the middle of a defun.  You'd be surprised how often that happens.
> That's what C-x C-e is for, and I'd bet my entire life savings on the
> rest of the Emacs team agreeing here.

I'd agree, but I also think that maybe the OP has a point: C-x C-e when
used after an expression such as (defvar foo 1) should, just like C-M-x
force `foo' to be reset to 1.


        Stefan

Re: Change the default binding of C-x C-e ?

[Andreas Röhler]

Am Sonntag, 6. Januar 2008 21:35 schrieb Stefan Monnier:
> > It is sometimes useful whilst hacking lisp to evaluate an expression in
> > the middle of a defun.  You'd be surprised how often that happens.
> > That's what C-x C-e is for, and I'd bet my entire life savings on the
> > rest of the Emacs team agreeing here.
>
> I'd agree, but I also think that maybe the OP has a point: C-x C-e when
> used after an expression such as (defvar foo 1) should, just like C-M-x
> force `foo' to be reset to 1.
>
>
>         Stefan
>

Would welcome that.

Presently, while playing around with new code, `devfar'
is not comfortable, as it defends it's value once set.

If values are still experimental, I use `setq'
instead. From what follows a need to correct that
afterwards. With this changing we would get rid of that
need and avoid possible errors.

Right?

Andreas Röhler

Re: Change the default binding of C-x C-e ?

[Richard Stallman]

    I think it is a good idea to change the default key-binding of C-x C-e to e=
    val-defun.

Since eval-defun is already on C-M-x, I don't see a point putting it
on C-x C-e as well.

Re: Change the default binding of C-x C-e ?

[Robert J. Chassell]

    Things worked fine until I progressed in elisp to where I wanted
    to use defvar.

(info "(eintr)defvar")
says

       The `defvar' special form ... only sets the value of the
    variable if the variable does not already have a value.

I just checked this:  I can use C-x C-e (eval-last-sexp) to set the
value of a variable with `defvar' for the first time.  As described in
the Introduction, I cannot change the value a second time with
`defvar' and `eval-last-sexp'; for that, I must use `setq'.

Today's GNU Emacs CVS snapshot, Sun, 2008 Jan  6  11:10 UTC
GNU Emacs 23.0.50.21 (i686-pc-linux-gnu, GTK+ Version 2.12.1)

--
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Re: Change the default binding of C-x C-e ?

[Tom Tromey]

Robert> I just checked this:  I can use C-x C-e (eval-last-sexp) to set the
Robert> value of a variable with `defvar' for the first time.  As described in
Robert> the Introduction, I cannot change the value a second time with
Robert> `defvar' and `eval-last-sexp'; for that, I must use `setq'.

For interactive elisp hacking I redefine eval-last-sexp to treat a
defvar more like a defconst.  This is pretty handy since it means I
don't have to modify the source or copy/paste/modify sexps in order to
do what I (usually) want.

Tom

Re: Change the default binding of C-x C-e ?

[Stephen J. Turnbull]

Tom Tromey writes:

 > For interactive elisp hacking I redefine eval-last-sexp to treat a
 > defvar more like a defconst.  This is pretty handy since it means I
 > don't have to modify the source or copy/paste/modify sexps in order to
 > do what I (usually) want.

XEmacs's eval-last-sexp also does this (by default) and issues a
warning that the defvar has been treated as a defconst.

As a possibly useful data point, I do not recall seeing a complaint
about this (I've been following the XEmacs developer's list
religiouusly and the newsgroup intermittently since 1997).