RE: Meta-code confusion

[Doug Lewan]

Well, after a few more hours I have a work-around. I think the original problem 
was because (defvar) is a special form, but I'm still not sure.

The current work-around is to build a string that looks right and then (eval 
(read THAT-STRING)) and let the results of that be the return value. I can't 
see the interesting difference, but it does what I want.

,Doug

> -----Original Message-----
> From: help-gnu-emacs-bounces+dougl=shubertticketing.com@gnu.org
> [mailto:help-gnu-emacs-bounces+dougl=shubertticketing.com@gnu.org] On
> Behalf Of Doug Lewan
> Sent: Friday, 2012 August 10 15:12
> To: help-gnu-emacs@gnu.org
> Subject: Meta-code confusion
> 
> I have development environment that has a handful of files with
> isomorphic (but not identical) structures.
> I'd like to use the same code to define modes for all of them, but
> clearly there are things I don't understand about writing meta-code in
> emacs lisp.
> 
> As a starting point I'm failing with the following:
> 
> (defvar *pp-symbol-re* "\\(?:\\s_\\|\\sw\\)")
> (defun ppm-define-vars (name abbreviation)
>   "Build a list of vars for the new mode."
>   (let* ((start-var-name (format "*pp-%s-start-re*" abbreviation))
>        (start-var (make-symbol start-var-name))
>        (start-re (list 'concat (format "^%s\\s-+" name) '*pp-symbol-
> re*)))
>     (list (list 'defvar start-var start-re))))
> 
> I want all such functions to return a list of definitions of the type
> of interest.
> This one happens to return a list of one element, [I would like] a
> variable definition.
> It certainly looks like it's returning the right kind of thing:
> 
> (car (ppm-define-vars "douglas" "dug"))
> => (defvar *pp-dug-start-re* (concat "^douglas\\s-+" *pp-symbol-re*))
> 
> And (eval) looks like it does the right thing:
> (eval (car (ppm-define-vars "douglas" "dug")))
> => *pp-dug-start-re*
> 
> (defvar) returns a symbol and (symbolp) confirms that that is a symbol.
> 
> However, using *pp-dug-start-re* gets a void-variable error.
> On the other hand
> (boundp (eval (car (ppm-define-vars "douglas" "dug"))))
> => t
> which would seem to be a contradiction.
> 
> I'm using
> GNU Emacs 24.1.1 (i686-pc-cygwin, GTK+ Version 2.24.10) of 2012-07-17
> on fiona    and
> GNU Emacs 24.1.1 (powerpc-ibm-aix6.1.0.0, X toolkit, Xaw scroll bars)
> of 2012-07-25 on devlpar1.
> 
> I would gladly pay with a beer¹ to understand this better.
> 
> ,Douglas
> Douglas Lewan
> Shubert Ticketing
> (201) 489-8600 ext 224
> 
> There is no national science just as there is no national
> multiplication table; what is national is no longer science. - Anton
> Checov
> _____________
> ¹ "beer" is a variable, replace it with an appropriate value should
> beer be distasteful to you or otherwise inappropriate.
>