Re: save-restriction, save-excursion

[pokerface <pokerface@use.net>]

Thank you gentlemen for the helpful replies!

Ryan Yeske <rcyeske@vcn.bc.ca> wrote in
news:87fzw9ceye.fsf@cut.hotdog.tmp: 

> David Kastrup <David.Kastrup@t-online.de> writes:
> 
>> Ryan Yeske <rcyeske+spam@vcn.bc.ca> writes:
>> 
>> > From the node "Narrowing" in the elisp manual:
>> > 
>> >      `save-restriction' does _not_ restore point and the mark; use
>> >      `save-excursion' for that.  If you use both `save-restriction'
>> >      and `save-excursion' together, `save-excursion' should come
>> >      first (on the outside).  Otherwise, the old point value would
>> >      be restored with temporary narrowing still in effect.  If the
>> >      old point value were outside the limits of the temporary
>> >      narrowing, this would fail to restore it accurately.
>> 
>> Hmmm.  What if I have a restriction active and write
>> (save-excursion
>>   (save-restriction
>>     (widen)
>>     (goto (point-min))))
>> 
>> When the restriction gets restored, point will lie outside of the
>> restored restriction.  Wouldn't that cause trouble?
> 
> Try it :)
> 
> It helps me to think about it like this:
> 
> 1) save the point
> 2) save the restriction
> 3) frob the restriction (narrow *or* widen)
> 4) frob the point
> 5) restore the old restriction
> 6) restore the old point
>  
> It doesn't matter whether you are widening or narrowing.  When the
> restriction is restored (step 5), the point is adjusted to be within
> the restriction (the point can never be outside the current
> restriction).  It doesn't really matter though, since the point is
> then immediatly restored to the initial value within the initial
> restriction at step 6.
> 
> Ryan
>