two ways of adding a path to the list variable load-path. equivalent?

two ways of adding a path to the list variable load-path. equivalent?

[Nobuko Three]

1.
(setq load-path (cons "~/elisp/" load-path))

2.
(add-to-list 'load-path "~/elisp/")

Are there any situation where one would prefer one over another?
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Re: two ways of adding a path to the list variable load-path. equivalent?

[Peter Dyballa]

Am 19.05.2009 um 19:33 schrieb Nobuko Three:

> (setq load-path (cons "~/elisp/" load-path))
>
> 2.
> (add-to-list 'load-path "~/elisp/")


The latter does *not* add the new element on top when this element  
already exists somewhere in the list. So the latter form is preferable.

--
Greetings

   Pete

Hard Disk, n.:
	A device that allows users to delete vast quantities
	of data with simple mnemonic commands.

Re: two ways of adding a path to the list variable load-path. equivalent?

[Kevin Rodgers]

Peter Dyballa wrote:
> 
> Am 19.05.2009 um 19:33 schrieb Nobuko Three:
> 
>> (setq load-path (cons "~/elisp/" load-path))
>>
>> 2.
>> (add-to-list 'load-path "~/elisp/")
> 
> 
> The latter does *not* add the new element on top when this element 
> already exists somewhere in the list. So the latter form is preferable.

Unless the intent is to make sure the element is first in the list.

-- 
Kevin Rodgers
Denver, Colorado, USA

Re: two ways of adding a path to the list variable load-path. equivalent?

[Ralf Mattes]

On Tue, 19 May 2009 10:33:09 -0700, Nobuko Three wrote:

> 1.
> (setq load-path (cons "~/elisp/" load-path))
> 
> 2.
> (add-to-list 'load-path "~/elisp/")
> 
> Are there any situation where one would prefer one over another?

The setq way will always add a new value to the list while add-to-list
will only add a value iff it's not already present in the list.
Usually one wants to have have a path only once in the load-path.

 HTH Ralf Mattes

Re: two ways of adding a path to the list variable load-path. equivalent?

[Nikolaj Schumacher]

Nobuko Three <nbko3@yahoo.com> wrote:

> 1.
> (setq load-path (cons "~/elisp/" load-path))
>
> 2.
> (add-to-list 'load-path "~/elisp/")
>
> Are there any situation where one would prefer one over another?

As you probably know from the documentation of add-to-list, it will test
whether the directory is already included before adding it another time.

The downside of add-to-list is, adding the path will be slightly slower (and
increasingly slower with the size of the list).  The downside of consing
is that duplicates might slow down loading a bit.

I'd suggest add-to-list, but the difference is negligible.


regards,
Nikolaj Schumacher