Another lisp question

Another lisp question

[Klaus Jantzen]

Hi,

in an interactive function I have

(interactive  "sEnter number: ")

When hitting <Enter> without entering anything, emacs comes back to the 
input request.
How can I find out, that nothing has been entered so that I can use e.g. 
a default value?

Thanks for a pointer.

-- 

K.D.J.

RE: Another lisp question

[Drew Adams]

> (interactive  "sEnter number: ")

Consider using `read-number':

(interactive (list (read-number "Number: " 42)))

> When hitting <Enter> without entering anything, emacs comes 
> back to the input request. How can I find out, that nothing
> has been entered so that I can use e.g. a default value?

I don't understand how that happens to you.
It should just return the empty string, "".

M-: (defun foo (arg) (interactive "sNum: ") (message "%S" arg))
M-x foo RET RET

That returns "" for me.

Re: Another lisp question

[Klaus Jantzen]

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RE: Another lisp question

[Drew Adams]

	(defun mytest (n)
	  " Test"
	  ; (interactive "nEnter number: ")
	  (interactive (list (read-number "Enter number: ")))
	  (message "%d was entered" n))
	
	With both versions of the interactive statement I have the
      same effect: the prompt comes back as long as I do not enter anything.
	
	I am running emacs22 on Debian lenny.
	Do I need a special setting to achive what I want?

You said you wanted to use the default value if the user hit Return with typing
anything first. For that, use (read-number "Number: " MY-DEFAULT), as I
suggested before.

Re: Another lisp question

[Klaus Jantzen]

Drew Adams wrote:
> 	(defun mytest (n)
> 	  " Test"
> 	  ; (interactive "nEnter number: ")
> 	  (interactive (list (read-number "Enter number: ")))
> 	  (message "%d was entered" n))
> 	
> 	With both versions of the interactive statement I have the
>       same effect: the prompt comes back as long as I do not enter anything.
> 	
> 	I am running emacs22 on Debian lenny.
> 	Do I need a special setting to achive what I want?
>
> You said you wanted to use the default value if the user hit Return with typing
> anything first. For that, use (read-number "Number: " MY-DEFAULT), as I
> suggested before.
>
>
>   
OK; I did not really understand why you had that 42 in your code.
It works.
Thank you.
-- 

K.D.J.

Re: Another lisp question

[Suvayu Ali]

On Friday 16 April 2010 09:31 AM, Klaus Jantzen wrote:
> Drew Adams wrote:
>> (defun mytest (n)
>> " Test"
>> ; (interactive "nEnter number: ")
>> (interactive (list (read-number "Enter number: ")))
>> (message "%d was entered" n))
>>
>> With both versions of the interactive statement I have the
>> same effect: the prompt comes back as long as I do not enter anything.
>>
>> I am running emacs22 on Debian lenny.
>> Do I need a special setting to achive what I want?
>>
>> You said you wanted to use the default value if the user hit Return
>> with typing
>> anything first. For that, use (read-number "Number: " MY-DEFAULT), as I
>> suggested before.
>>
>>
> OK; I did not really understand why you had that 42 in your code.
> It works.
> Thank you.

I believe its the answer to the ultimate question? ;)

-- 
Suvayu

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