Re: Tabs and Spaces

[pjb@informatimago.com (Pascal J. Bourguignon)]

use.address@my.homepage.invalid (Chris Gordon-Smith) writes:

> Pascal J. Bourguignon <pjb@informatimago.com> wrote:
>> use.address@my.homepage.invalid (Chris Gordon-Smith) writes:
>> 
>>> Hello All
>>>
>>> I have recenly started using emacs for programming, after years using 
>>> KDevelop. One problem I have is indenting code. I have my own indentation 
>>> style. and ideally I would like to setup emacs to support it automatically. 
>>> However, in the short term I'll settle for having emacs convert a TAB 
>>> keypress into the correct number of spaces to fill whitespace up to the 
>>> next tabstop.
>>>
>>> At the moment I have
>>>
>>> (global-set-key (kbd "TAB") 'self-insert-command) 
>>>
>>> in my .emacs to force insertion of a tab, but I have to keep invoking 
>>> untabify manually (otherwise my code looks misaligned when I upload it to 
>>> Google Code).
>>>
>>> Can anyone help.
>> 
>> You shouldn't insert TAB, this is very bad.  At the very least, you
>> may compute the number of spaces you need to insert and insert them
>> rather.
> Yes, that's what I would like to do. Can you suggest how to do this. Do I 
> need to put something in my .emacs file. What would it look like?
>
>> 
>> But depending on the language you use, a different mode will be used
>> to edit your source and each mode may provide its own indenting rules.
>> 
>> In the case of Lisp, you may add a indent-function property to the
>> plist of the operator name.
>> 
>> In the case of C, you may customize the variable: c-offsets-alist. See
>> also: c-style-alist ; perhaps there's already a style defined that
>> you'll like.


In my post, there was a subliminal question, but it didn't reach your
consciousness, I'm sorry.  Here it is:

   What programming language do you use?

Depending on the answer you give, you may well have nothing to program.
Otherwise, you could do something like this:

(defconst +space+ 32 "ASCII code for the space character")

(defun my-language/indent-line ()
   (interactive) 
   (let ((where (let ((m (make-marker))) (set-marker m (point)) m))
         (indent (my-language/get-indent-from-some-parsing-around (point))))
      (beginning-of-line)
      (looking-at "^[ \t]*")
      (delete-region (beginning-of-line) (match-end))
      (goto-char (beginning-of-line))
      (insert (make-string indent +space+))
      (goto-char where)
      (set-marker where nil)))


(local-set-key (kbd "TAB") 'my-language/indent-line)


Of course, all the difficulty (or simplicity, depends on your language)
is in implementing my-language/get-indent-from-some-parsing-around.


-- 
__Pascal Bourguignon__