all messages for Emacs-related lists mirrored at yhetil.org
 help / color / mirror / code / Atom feed
* About features
@ 2013-03-06 10:08 Xue Fuqiao
  2013-03-06 10:48 ` Andreas Röhler
  2013-03-06 14:28 ` Kevin Rodgers
  0 siblings, 2 replies; 7+ messages in thread
From: Xue Fuqiao @ 2013-03-06 10:08 UTC (permalink / raw)
  To: help-gnu-emacs

In (info "(elisp) Coding Conventions"):

    * Put a call to `provide' at the end of each separate Lisp file.
      *Note Named Features::.

    * If a file requires certain other Lisp programs to be loaded
      beforehand, then the comments at the beginning of the file should
      say so.  Also, use `require' to make sure they are loaded.  *Note
      Named Features::.

Why should we use `provide' and `require'?  Is 
`load'/`load-library'/`load-file' enough?  Thanks.

-- 
Best regards, Xue Fuqiao.
http://www.emacswiki.org/emacs/XueFuqiao



^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: About features
       [not found] <mailman.21537.1362564509.855.help-gnu-emacs@gnu.org>
@ 2013-03-06 10:42 ` Barry Margolin
  0 siblings, 0 replies; 7+ messages in thread
From: Barry Margolin @ 2013-03-06 10:42 UTC (permalink / raw)
  To: help-gnu-emacs

In article <mailman.21537.1362564509.855.help-gnu-emacs@gnu.org>,
 Xue Fuqiao <xfq.free@gmail.com> wrote:

> In (info "(elisp) Coding Conventions"):
> 
>     * Put a call to `provide' at the end of each separate Lisp file.
>       *Note Named Features::.
> 
>     * If a file requires certain other Lisp programs to be loaded
>       beforehand, then the comments at the beginning of the file should
>       say so.  Also, use `require' to make sure they are loaded.  *Note
>       Named Features::.
> 
> Why should we use `provide' and `require'?  Is 
> `load'/`load-library'/`load-file' enough?  Thanks.

`require' doesn't reload the file if it has already been loaded.

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***


^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: About features
  2013-03-06 10:08 About features Xue Fuqiao
@ 2013-03-06 10:48 ` Andreas Röhler
  2013-03-06 14:28 ` Kevin Rodgers
  1 sibling, 0 replies; 7+ messages in thread
From: Andreas Röhler @ 2013-03-06 10:48 UTC (permalink / raw)
  To: help-gnu-emacs

Am 06.03.2013 11:08, schrieb Xue Fuqiao:
> In (info "(elisp) Coding Conventions"):
>
>     * Put a call to `provide' at the end of each separate Lisp file.
>       *Note Named Features::.
>
>     * If a file requires certain other Lisp programs to be loaded
>       beforehand, then the comments at the beginning of the file should
>       say so.  Also, use `require' to make sure they are loaded.  *Note
>       Named Features::.
>
> Why should we use `provide' and `require'?  Is `load'/`load-library'/`load-file' enough?  Thanks.
>

IMHO `provide' delivers a kind of city-map with street-names, which exists, before you will visit a street.
Also require, before you a looking for the location of a certain building, checks if the
street-in-my-example exists.



^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: About features
  2013-03-06 10:08 About features Xue Fuqiao
  2013-03-06 10:48 ` Andreas Röhler
@ 2013-03-06 14:28 ` Kevin Rodgers
  1 sibling, 0 replies; 7+ messages in thread
From: Kevin Rodgers @ 2013-03-06 14:28 UTC (permalink / raw)
  To: help-gnu-emacs

On 3/6/13 3:08 AM, Xue Fuqiao wrote:
> In (info "(elisp) Coding Conventions"):
>
> * Put a call to `provide' at the end of each separate Lisp file.
> *Note Named Features::.
>
> * If a file requires certain other Lisp programs to be loaded
> beforehand, then the comments at the beginning of the file should
> say so. Also, use `require' to make sure they are loaded. *Note
> Named Features::.
>
> Why should we use `provide' and `require'? Is `load'/`load-library'/`load-file'
> enough? Thanks.

`provide' allows you to `require' unconditionally, but the library/file will 
only be loaded if necessary.

-- 
Kevin Rodgers
Denver, Colorado, USA




^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: About features
@ 2013-03-06 22:21 Xue Fuqiao
  0 siblings, 0 replies; 7+ messages in thread
From: Xue Fuqiao @ 2013-03-06 22:21 UTC (permalink / raw)
  To: help-gnu-emacs


>> Why should we use `provide' and `require'? Is `load'/`load-library'/`load-file'
>> enough? Thanks.
>
> `provide' allows you to `require' unconditionally, but the library/file will
> only be loaded if necessary.

Why?  Can you explain it more detailed?

-- 
Best regards, Xue Fuqiao.
http://www.emacswiki.org/emacs/XueFuqiao



^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: About features
       [not found] <mailman.21593.1362608491.855.help-gnu-emacs@gnu.org>
@ 2013-03-06 23:55 ` Barry Margolin
  0 siblings, 0 replies; 7+ messages in thread
From: Barry Margolin @ 2013-03-06 23:55 UTC (permalink / raw)
  To: help-gnu-emacs

In article <mailman.21593.1362608491.855.help-gnu-emacs@gnu.org>,
 Xue Fuqiao <xfq.free@gmail.com> wrote:

> >> Why should we use `provide' and `require'? Is 
> >> `load'/`load-library'/`load-file'
> >> enough? Thanks.
> >
> > `provide' allows you to `require' unconditionally, but the library/file 
> > will
> > only be loaded if necessary.
> 
> Why?  Can you explain it more detailed?

Why don't you just look at the source code? Simplifying, it's something 
like:

(defun require (feature)
  (if (not (member feature features))
      (load feature)))

(defun provide (feature)
  (if (not (member feature features))
      (push feature features)))

As I said in my earlier response: require won't reload a library if it's 
already been loaded, and it uses the features variable to keep track of 
which libraries have been loaded this way.

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***


^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: About features
@ 2013-03-07 12:47 Xue Fuqiao
  0 siblings, 0 replies; 7+ messages in thread
From: Xue Fuqiao @ 2013-03-07 12:47 UTC (permalink / raw)
  To: help-gnu-emacs

>>>> Why should we use `provide' and `require'? Is
>>>> `load'/`load-library'/`load-file'
>>>> enough? Thanks.

>>> `provide' allows you to `require' unconditionally, but the library/file
>>> will
>>> only be loaded if necessary.

>> Can you explain it more detailed?

> Simplifying, it's something like:

> (defun require (feature)
>   (if (not (member feature features))
>       (load feature)))

> (defun provide (feature)
>   (if (not (member feature features))
>       (push feature features)))

> As I said in my earlier response: require won't reload a library if it's
> already been loaded, and it uses the features variable to keep track of
> which libraries have been loaded this way.

I see.  Thanks, I misunderstood your meaning before. (My English sucks.)

-- 
Best regards, Xue Fuqiao.
http://www.emacswiki.org/emacs/XueFuqiao



^ permalink raw reply	[flat|nested] 7+ messages in thread

end of thread, other threads:[~2013-03-07 12:47 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2013-03-06 10:08 About features Xue Fuqiao
2013-03-06 10:48 ` Andreas Röhler
2013-03-06 14:28 ` Kevin Rodgers
     [not found] <mailman.21537.1362564509.855.help-gnu-emacs@gnu.org>
2013-03-06 10:42 ` Barry Margolin
  -- strict thread matches above, loose matches on Subject: below --
2013-03-06 22:21 Xue Fuqiao
     [not found] <mailman.21593.1362608491.855.help-gnu-emacs@gnu.org>
2013-03-06 23:55 ` Barry Margolin
2013-03-07 12:47 Xue Fuqiao

Code repositories for project(s) associated with this external index

	https://git.savannah.gnu.org/cgit/emacs.git
	https://git.savannah.gnu.org/cgit/emacs/org-mode.git

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.