check to see if a buffer with a certain name exists?

check to see if a buffer with a certain name exists?

[Matt Price]

hi folks,

first thanks to everyone who's answered my question about mail, i'm
going to be back to that in a second.  

but in the meantime:  i want to be able to check if there's a buffer
open named *Mutt* .  what's the best way to do this?  in python, for
instance, i would just say:


if "*Mutt*" in buffer-list :
	return true
else :
	return false

in lisp i'm not seeing a quick way to test for something like this.
best i can see right now is to use dolist thus:

(dolist (name (buffer-list) foundit)
  (let ((foundit 0))
    (if (string-match "*scratch*" name)
    (setq foundit 1))
)
)

which isn't quite right, i have a variabletype mismatch.  i'd love some
help -- still having trouble navigating the documentation... thanks
again,
matt




-- 
Matt Price
matt.price@utoronto.ca

RE: check to see if a buffer with a certain name exists?

[Drew Adams]

> i want to be able to check if there's a buffer
> open named *Mutt* .  what's the best way to do this?  in python, for
> instance, i would just say:
> if "*Mutt*" in buffer-list : return true else : return false
> in lisp i'm not seeing a quick way to test for something like this.

C-h f get-buffer

(get-buffer "*Mutt*")

The Elisp manual is your friend. In the manual, `i buffer RET' takes you to the
Buffers chapter. Buffer Names in the menu there shows you this:

    Function: get-buffer buffer-or-name
     This function returns the buffer specified by BUFFER-OR-NAME.  If
     BUFFER-OR-NAME is a string and there is no buffer with that name,
     the value is `nil'.  If BUFFER-OR-NAME is a buffer, it is returned
     as given; that is not very useful, so the argument is usually a
     name.  For example:

          (setq b (get-buffer "lewis"))
               => #<buffer lewis>
          (get-buffer b)
               => #<buffer lewis>
          (get-buffer "Frazzle-nots")
               => nil

     See also the function `get-buffer-create' in *note Creating
     Buffers::.

Re: check to see if a buffer with a certain name exists?

[Nikolaj Schumacher]

Matt Price <matt.price@utoronto.ca> wrote:

> in lisp i'm not seeing a quick way to test for something like this.
> best i can see right now is to use dolist thus:
>
> (dolist (name (buffer-list) foundit)
>   (let ((foundit 0))
>     (if (string-match "*scratch*" name)
>     (setq foundit 1))
> )
> )

Drew already gave you the cleaner way.  Let me also tell you, why yours
is not working.

First, you bind foundit inside the `dolist' body.  The value is lost when
the `let' block exits, and the variable is undefined.

Second, `buffer-list' returns buffer "objects", not strings.

Here's how it would work:

(let ((foundit 0))
  (dolist (name (buffer-list) foundit)
    (if (string-match "*scratch*" (buffer-name name))
        (setq foundit 1))))

Or the Awesome Lisp Way(TM):

(member "*scratch*" (mapcar 'buffer-name (buffer-list)))




regards,
Nikolaj Schumacher

Re: check to see if a buffer with a certain name exists?

[Ian Eure]

On Nov 13, 2008, at 11:50 AM, Nikolaj Schumacher wrote:

> Matt Price <matt.price@utoronto.ca> wrote:
>
>> in lisp i'm not seeing a quick way to test for something like this.
>> best i can see right now is to use dolist thus:
>>
>> (dolist (name (buffer-list) foundit)
>>  (let ((foundit 0))
>>    (if (string-match "*scratch*" name)
>>    (setq foundit 1))
>> )
>> )
>
> Drew already gave you the cleaner way.  Let me also tell you, why  
> yours
> is not working.
>
> First, you bind foundit inside the `dolist' body.  The value is lost  
> when
> the `let' block exits, and the variable is undefined.
>
> Second, `buffer-list' returns buffer "objects", not strings.
>
> Here's how it would work:
>
> (let ((foundit 0))
>  (dolist (name (buffer-list) foundit)
>    (if (string-match "*scratch*" (buffer-name name))
>        (setq foundit 1))))
>
> Or the Awesome Lisp Way(TM):
>
> (member "*scratch*" (mapcar 'buffer-name (buffer-list)))
>
Is there something wrong with:

(get-buffer "*Mutt*")

...which returns the #buffer object?

Or if you really care about t/nil, you can do:

(bufferp (get-buffer "*Mutt*"))

  - Ian

RE: check to see if a buffer with a certain name exists?

[Matt Price]

On Thu, 2008-11-13 at 08:45 -0800, Drew Adams wrote:
> > i want to be able to check if there's a buffer
> > open named *Mutt* .  what's the best way to do this?  in python, for
> > instance, i would just say:
> > if "*Mutt*" in buffer-list : return true else : return false
> > in lisp i'm not seeing a quick way to test for something like this.
> 
> C-h f get-buffer
> 
> (get-buffer "*Mutt*")
> 
> The Elisp manual is your friend. In the manual, `i buffer RET' takes you to the
> Buffers chapter. Buffer Names in the menu there shows you this:
> 
>     Function: get-buffer buffer-or-name
>      This function returns the buffer specified by BUFFER-OR-NAME.  If
>      BUFFER-OR-NAME is a string and there is no buffer with that name,
>      the value is `nil'.  If BUFFER-OR-NAME is a buffer, it is returned
>      as given; that is not very useful, so the argument is usually a
>      name.  For example:
> 
>           (setq b (get-buffer "lewis"))
>                => #<buffer lewis>
>           (get-buffer b)
>                => #<buffer lewis>
>           (get-buffer "Frazzle-nots")
>                => nil
> 
>      See also the function `get-buffer-create' in *note Creating
>      Buffers::.
> 
thanks Drew!  i am still getting used to info, thanks.  i had looked up
buffers inthe online manual but missed get-buffer, clearly it's exactly
what i'm looking for, thanks again!

matt


-- 
Matt Price
matt.price@utoronto.ca

Re: check to see if a buffer with a certain name exists?

[Matt Price]

On Thu, 2008-11-13 at 20:50 +0100, Nikolaj Schumacher wrote:
> (member "*scratch*" (mapcar 'buffer-name (buffer-list)))

wow, i really like the Awesome LISP Way (TM).  thanks for the debugging
help...

matt

-- 
Matt Price
matt.price@utoronto.ca