Re: empty-line-p

[Andreas Roehler <andreas.roehler@easy-emacs.de>]

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