re-defvar a variable without reloading emacs

re-defvar a variable without reloading emacs

[ken]

I've got a defvar'd variable in my .emacs which I want to redefine.  But
rerunning (defvar somevar "someval") doesn't work... according to the
docs, this is the correct behavior.  So is there some way to redefine
this variable without reloading the whole of emacs?

Thanks vielmals.

-- 
"To make an apple pie from scratch,
first create the universe."
        -- Carl Sagan

Re: re-defvar a variable without reloading emacs

[Eli Zaretskii]

> Date: Sat, 13 Jun 2009 08:51:11 -0400
> From: ken <gebser@mousecar.com>
> Reply-To: gebser@mousecar.com
> 
> 
> I've got a defvar'd variable in my .emacs which I want to redefine.  But
> rerunning (defvar somevar "someval") doesn't work... according to the
> docs, this is the correct behavior.  So is there some way to redefine
> this variable without reloading the whole of emacs?

Use setq.

RE: re-defvar a variable without reloading emacs

[Drew Adams]

> > I've got a defvar'd variable in my .emacs which I want to 
> > redefine.  But rerunning (defvar somevar "someval") doesn't work... 
> > according to the docs, this is the correct behavior.  So is there
> > some way to redefine this variable without reloading the whole of emacs?
> 
> Use setq.

It depends what is meant:

1. If you mean that you have already evaluated (e.g. loaded) the code
(defvar somevar "someval"), and you have now edited that code to
(defvar somevar "newval"), and you want to evaluate that
interactively, see node `Evaluating Emacs Lisp Expressions' in the
Emacs manual. It says you can put the cursor somewhere on the
expression and hit `C-M-x', to do what you want.

2. If you mean that you have want to be able to evaluate (e.g. load)
the code (defvar somevar "someval") and then evaluate (load) some
other code that redefines `somevar', then use (setq somevar "newval")
as that other code.

`setq' always assigns a value. `defvar' assigns a value only the
first time it is evaluated, normally, but `C-M-x' overrides this,
making it assign a value again.

Re: re-defvar a variable without reloading emacs

[ken]

Drew,

Excellent answer... 400% better than an expert's... it reminds us that
the meaning of "guru" is "teacher".

But much thanks to all who replied.


On 06/13/2009 11:19 AM Drew Adams wrote:
>>> I've got a defvar'd variable in my .emacs which I want to 
>>> redefine.  But rerunning (defvar somevar "someval") doesn't work... 
>>> according to the docs, this is the correct behavior.  So is there
>>> some way to redefine this variable without reloading the whole of emacs?
>> Use setq.
> 
> It depends what is meant:
> 
> 1. If you mean that you have already evaluated (e.g. loaded) the code
> (defvar somevar "someval"), and you have now edited that code to
> (defvar somevar "newval"), and you want to evaluate that
> interactively, see node `Evaluating Emacs Lisp Expressions' in the
> Emacs manual. It says you can put the cursor somewhere on the
> expression and hit `C-M-x', to do what you want.
> 
> 2. If you mean that you have want to be able to evaluate (e.g. load)
> the code (defvar somevar "someval") and then evaluate (load) some
> other code that redefines `somevar', then use (setq somevar "newval")
> as that other code.
> 
> `setq' always assigns a value. `defvar' assigns a value only the
> first time it is evaluated, normally, but `C-M-x' overrides this,
> making it assign a value again.
> 
> 
> 

Re: re-defvar a variable without reloading emacs

[Markus Triska]

ken <gebser@mousecar.com> writes:

> I've got a defvar'd variable in my .emacs which I want to redefine.  But
> rerunning (defvar somevar "someval") doesn't work

Use C-M-x (`eval-defun') on the form instead; from its docstring:

   If the current defun is actually a call to `defvar' or `defcustom',
   evaluating it this way resets the variable using its initial value
   expression even if the variable already has some other value.