Re: [Proposal] M-x tabify to indent only when needed.

[Stefan Monnier <monnier@iro.umontreal.ca>]

>>> +          (if (= (/ end-col tab-width) (/ beg-col tab-width))
>>> +              ;; The spacing does not straddle a TAB boundary, so we won't
>>> +              ;; be able to use a TAB here anyway: there's nothing to do.
>>> +              nil
>> 
>>> This detects a case where no tabs can be used.
>>> It doesn't detect the case where tabs already ARE used.
>> 
>> Those cases aren't matched by the regexp.
>> 
>>> -(defvar tabify-regexp "[ \t][ \t]+"
>>> +(defvar tabify-regexp " [ \t]+"
>> 
>>> Is that change supposed to exclude those other cases?
>> 
>> Exactly.
>> 
>> Stefan

> IIUC,  your  patch does  work  and is  very  much  clearer than  mine.
> However, it suffers from the same precondition on tabify-regexp, which
> should be described in its docstring.

Another regexp will also work, except that it may result in "spurious"
buffer modifications.  But people have lived with such spurious buffer
modifications until now, so it's not a big deal, is it?


        Stefan