Re: empty-line-p

[Andreas Roehler]

David Hansen schrieb:
> On 29 Mar 2007 14:32:05 GMT Joost Kremers wrote:
>
>   
> > Andreas Roehler wrote:
> >     
> > > needed a check at several occassions, if the current line
> > > contains printable characters.
> > >
> > > What about the following to solve this?
> > >
> > > (defun empty-line-p ()
> > >   "Returns t if cursor is at an empty line "
> > >   (interactive)
> > >   (save-excursion
> > >     (beginning-of-line)
> > >   (if
> > >       (looking-at "^[ \t\f\r]*$")
> > >       t
> > >     nil)))
> > >       
> > you don't need the if-statement here:
> >
> > (defun empty-line-p ()
> >   "Returns t if cursor is at an empty line "
> >   (interactive)
> >   (save-excursion
> >     (beginning-of-line)
> >     (looking-at "^[ \t\f\r]*$")))
> >
> > looking-at already returns t or nil.
> >     
>
> And to avoid some painful bug hunting (happened to me with nearly
> the same code)
What about to collect minor tools like this somewhere?

>  wrap it in a `save-match-data'.
>
> David
>   

OK, thanks. So I got this now:

(defcustom empty-line-p-chars "^[ \t\f\r]*$"
 "empty-line-p-chars"
:type 'regexp
:group 'convenience)

(defun empty-line-p (&optional ispec)
 "Returns t if cursor is at an empty line, nil otherwise.
Displays result in minibuffer when called interactive."
 (interactive "p")
 (save-excursion
   (beginning-of-line)
   (save-match-data
     (when ispec
   (message "%s" (looking-at empty-line-p-chars)))
     (looking-at empty-line-p-chars))))


;;;;;

Andreas