I am trying to program GNU Emacs 23 to issue require commands lazily, on demand, instead of up front in my .emacs file. If I wanted to delay the execution of a load command, I could use autoload. But require and load take different sorts of arguments.
Is there a predefined function that does for require the same job that autoload does for load? And if not, what tools would people recommend that I use to roll my own?
There is not difference between require and load with regards to autoload. require is just a frontend to load, which more or less comes down to:
(defun require (feature &optional filename noerror)
(unless (featurep feature)
(let ((filename (or filename (symbol-name feature))))
(load filename noerror))))
As you can see, the symbol name given to require is equal to the filename given to load. As a matter of fact, the first (require 'foo) evaluated in an Emacs session is equivalent to (load "foo").
Thus, you can just use (auto-load 'foo-function "foo") for foo-function from the library foo, that you can load with (require 'foo).
One more answer to help clarify (this was a little verbose for a comment):
autoload says "if this function isn't already defined, then load this file (if and when the function is called)."
require says "if this library isn't already loaded, then load this file (immediately)."
Note in particular that you don't need to use require to load a library; that's simply the way you ensure that you don't load it again (assuming you don't want to do that). The (provide 'FEATURE) expression in the library will be evaluated no matter how the library was loaded, which lets any future require know that it doesn't need to do anything.
It's a similar situation for autoload -- if the file has already been loaded (and therefore the function in question properly defined), then the autoload no longer has any effect.
What kind of "demand" do you have in mind for your "on demand"?
If a given command or other function needs (or soft-needs) a given library, then that function itself can use (require 'foo) or (require 'foo nil t). The library will be loaded on demand from that function.
Consider also whether you might need to load the file more than once, i.e., reload it in some situations, whether or not it has already been loaded.
For #2, for instance, my code that uses a library of Lisp macros, icicles-mac.el does not just use require, because I want to make sure that if a user gets a new version of that library (e.g., downloads a new source version and byte-compiles it) then that new version is used whenever s?he byte-compiles another library that needs it. (This is important -- when a library of macros changes, other libraries that use those macros generally need to be recompiled after loading the new macros file.) For that, instead of just (require 'icicles-mac) I use this:
(eval-when-compile
(or (condition-case nil
(load-library "icicles-mac") ; Use load-library to ensure latest .elc.
(error nil))
(require 'icicles-mac))) ; Require, so can load separately if not on `load-path'.
Related
I am adding Customize support for a package that provides a couple of global mode-independent commands. As I do not want to load the package unless the user explicitly invokes the commands through keybindings yet I want to allow customization right after the user installs the package, I tried to use code like:
;;;###autoload
(defcustom foo-bar nil
"bar setting for for"
:type boolean)
;;;###autoload
(defun foo-command-1 () ...)
With that after I install the package I can invoke foo-command-1. I can also use customize-variable to set and save foo-bar. However, when I start Emacs again, the value of foo-bar is reset to default and Emacs complains that the value is changed outside customize.
AFAICS the reason for this is that the code that Emacs puts into the autoloads file for defcustom assumes that it will run before Emacs calls custom-set-variables in the init.el. However, this is not the case with a package which autoloads are run after the init file.
Is this a known problem? To workaround I replaced the above with something like:
;;;###autoload
(unless (fboundp 'foo-command-1)
(defcustom foo-bar nil
"bar setting for for"
:type boolean))
;;;###autoload
(defun foo-command-1 () ...)
That copies the whole defcustom definition into the autoloads and prevents running it the second time when the package is loaded for real. This works and saved options are properly restored. Still I am puzzled why ###autoload for defcustom does not do the right thing on its own.
Yes, what you did is a reasonable way to accomplish what you want. If you want to autoload a defcustom and you care about when it will be evaluated relative to other code, then you need to control that timing in some way. The way you chose is reasonable.
A user's init file can load custom-file at any point the user chooses. And if no custom-file is used it is still not sure at what point the part of the init-file code that is managed by Customize will be evaluated with respect to other parts that might depend on values that it sets.
As a general rule, you don't want to autoload variables.
Yes, it's a known problem, and there's no really good solution to it (each solution I could come up with had its own set of bugs/misbehaviors), which is why all I can say is "don't autoload variables, please".
Even in the case where it happens to do what you want, it's undesirable in my experience. It just has too many quirks and corner cases.
I have to write a game in Lisp. In order to make it clear, I wanted to split the code in different .lisp files.
How can I call a function out of a function in the other file?
E.g. file1.lisp has a function called function1 and file2.lisp has a function called function2.
How can I call function2 out of function1?
Thanks!
Just so you know, there are a variety of different Lisp systems. I'll post the answer for Common Lisp.
The naive way is to use (load "filename.lisp"), but that doesn't really work very well after a while. Therefore...
Common Lisp has a library called "ASDF", which handles packaging and file management. There's a bit of setup to ASDF.
Create directory where ASDF looks for files.
Add this information to my Lisp system's init file.
I use this in my .sbclrc file (assuming that I created a .asdf file in ~) :
(pushnew "~/.asdf/" asdf:*central-registry* :test #'equal)
I usually use a previously built ASDF file and then modify it.
Here's a sample ASDF file's contents:
(asdf:defsystem #:cl-linq
:depends-on ( #:alexandria #:anaphora)
:components ((:file "cl-linq"))
:name "cl-linq"
:version "0.1"
:maintainer "Paul Nathan"
:author "Paul Nathan"
:licence "LLGPL"
:description "CL LINQ style interface with strains of SQL"
:long-description
"DSL for managing and querying datasets in a SQL/LINQ style
syntax. cl-linq provides a simple and usable set of primitives to
make data examination straightforward. ")
I put this code in a file cl-linq.asd next to my source code (cl-linq.lisp from the component "cl-linq" in the defsystem) and then symlink the cl-linq.asd file to my ~/.asdf/ directory.
Within my cl-linq.lisp file I include this:
(defpackage :cl-linq
(:use
:common-lisp
:anaphora)
(:export
#:query
#:cl-linq-select))
(in-package :cl-linq)
So for your case, I would have 2 components; each with their own defpackage form, exporting the functions out that the other package needed.
For the examples, I've taken the code from CL-LINQ, a project of mine. You are quite free to use it as a template.
This is for Emacs Lisp (aka elisp)
Create a file at this location: ~/.emacs.d/init.el
Create a file at this location: ~/.emacs.d/file1.el
Create a file at this location: ~/.emacs.d/file2.el
Now, open up ~/.emacs.d/init.el and write (and then save):
(load "~/.emacs.d/file1.el")
(load "~/.emacs.d/file2.el")
(defun run-both-functions ()
(interactive)
(switch-to-buffer "*Messages*")
(first-function)
(sit-for 2)
(second-function))
Now, open up ~/.emacs.d/file1.el and write (and then save):
(defun first-function ()
(message "My name is Fred."))
Now, open up ~/.emacs.d/file2.el and write (and then save):
(defun second-function ()
(message "My name is George."))
Now, restart Emacs and type: M-x run-both-functions RET
Any functions that you put into any of the three (3) files mentioned above will be accessible to other functions. You will note that run-both-functions includes an (interactive) statement, which means that the user can call the function with M-x or a keyboard shortcut.
If you use the function load it can be useful to not specify the file type.
Loading files: fasl or source
Instead of (load "foo.lisp") one can call (load "foo"). Typically Common Lisp provides the feature of compiling Lisp files to fasl (fast load) files. Those are usually pre-compiled byte code or native code. Typically the Common Lisp implementation will load the compiled code if a file exists for it. This saves time (because compiled code usually can be loaded much faster than Lisp source code) and the code usually is faster (because a file compiler has compiled it).
Often one uses a function to load the compiled file if it is newer, or first compile the source file to a new compiled file.
Loading a file, based on the current file being loaded
In (load "foo") the file foo is not a complete filename. For example we don't know the directory where it is loaded from. This depends on things like the value of *default-pathname-defaults* or in some implementations on a current directory (typical for Unix systems). It may be useful to load the file based on the file we are currently loading - if loading one file triggers more files to be loaded. For this Common Lisp has the variables *load-pathname* and *load-truename* (which is the real filename as used with the filesystem).
To load a file foo in the same directory as the currently loaded file call:
(load (merge-pathnames "foo" *load-pathname*))
To load a file foo in a subdirectory bar of the same directory as the currently loaded file call:
(load (merge-pathnames "bar/foo" *load-pathname*))
With Common Lisp I done it like this:
In file1.lisp I define a function sayHello and export that function under the package name helloLisp
(defpackage :helloLisp
(:use :common-lisp)
(:export #:sayHello))
(in-package :helloLisp)
(defun sayHello () (print "Hello!"))
In the file file2.lisp I require this file like that:
(require "helloLisp" "./file1.lisp")
(helloLisp:sayHello)
Tested with SBCL 1.4.11
I want to load emacs init files faster, so I use the 'eval-after-load.
For example, when I load clojure file, I just put
(eval-after-load 'clojure-mode
'do-something)
It works.
But when I try
(eval-after-load 'emacs-lisp-mode
'do-something)
It doesn't work. I wonder to know the right major mode name of emacs-lisp.
Thanks.
Please read the documentation of eval-after-load:
eval-after-load LIBRARY FORM
This function arranges to evaluate form at the end of loading the file LIBRARY, each time LIBRARY is loaded. If LIBRARY is already loaded, it evaluates form right away. Don't forget to quote form!
[…] LIBRARY can also be a feature (i.e., a symbol), in which case form is evaluated at the end of any file where (provide LIBRARY) is called.
You have to pass the name of the file or library, which defines the major mode, as argument.
While some modes are defined in files of the same name (e.g. clojure-mode in clojure-mode.el), many files a different name, especially if the actually define multiple major modes.
emacs-lisp-mode is defined in lisp-mode.el, along with some other modes for Emacs Lisp editing (e.g. lisp-mode as a generic Lisp language mode, or lisp-interaction-mode for *scratch* buffers).
Hence, use (eval-after-load 'lisp-mode …)
Also, you have to give a single sexp as second argument, so you'll likely want to use (eval-after-load 'lisp-mode '(do-something)), to call the function do-something.
If you are using a snapshot build of Emacs, use with-eval-after-load, i.e. (with-eval-after-load 'lisp-mode (do-something)). It allows for more than a single form, and doesn't require quoting.
Just eval with M-: the variable major-mode. It actually is emacs-lisp-mode.
Note that *scratch* is actually in lisp-interaction-mode.
As to what you're trying to do, use (eval-after-load "lisp-mode").
As explained by #lunaryom, the arg passed to eval-after-load is not a function name but a feature name, which is basically a file name. So you need to find the name of the file from which the function is loaded.
We could provide a feature like eval-after-defun, and indeed it might be a good idea to do so. If you'd like such a thing, ask for it via M-x report-emacs-bug.
I want to load my file named "my-c-setup.el" when the c-mode is loading. So, I'm using the function "autoload".
With my python setup, it works well :
lang.el
(autoload 'python-mode "my-python-setup" "" t)
my-python-setup.el
(require 'python)
; ...
I'm trying to do the same with the c-mode, but i does not work :
lang.el
(autoload 'c-mode "my-c-setup" "" t)
my-c-setup.el
(setq c-basic-offset 4)
; ...
When I try to open a file in c-mode (test.c for example), I have the following error :
File mode specification error: (error "Autoloading failed to define function c-mode")
Autoload is not what you're looking for. What it does is simply load some code the first time it is needed, which is a handy way to extend Emacs' functionality while still keeping the start-up time low.
To solve your problem, we gotta think about what you really want to do: do you simply want some of your code to be loaded at some point, or do you want buffer-local customizations for ever buffer that is in c-mode?
If you simply want Emacs to load your code at start-up, either put your code directly into your .emacs file or use load-file or require instead of autoload:
load-file simply takes a file name, loads the lisp code in that file and evaluates it. So if your code is in a file named "/path/to/my-c-setup.el", you could put the following line in your .emacs, and the code will be loaded on every start-up:
(load-file "/path/to/my-c-setup.el")
Perhaps you don't want to give the absolute path name for every file you load. In that case, you could use the function load-library instead which is similar to load-file but tries to find the given filename in any of the directories stored in the variable load-path:
(add-to-list 'load-path "/path/to")
(load-library "my-c-setup.el")
The advantage is that you have to do the add-to-list part only once, and all subsequent calls to load-library will be able to find code in that directory.
An alternative way is the provide/require mechanism: you can make your .el-file "provide" some feature by putting a (provide 'feature) call in it, e.g.
(provide 'my-c-mode-customizations)
Then put an according (require 'feature) in your .emacs file, and your code will be loaded as well:
(require 'my-c-mode-customizations)
However, if you want your code only be loaded when c-mode is activated on a buffer, the way to achieve that is through Emacs' Hook mechanism:
A hook is a variable where you can
store a function or functions to be
called on a particular occasion by an
existing program.
Most major modes provide a customizable hook variable to which you can add functions that will be called whenever the major mode is invoked. For instance, c-mode provides c-mode-hook. In order for your own customizations to be called whenever c-mode is turned on for a buffer, put them in a function, say, my-c-mode-customizations and add the following line to your .emacs file:
(add-hook 'c-mode-hook 'my-c-mode-customizations)
Of course, you still need autoload for Emacs to actually find the definition of that function.
Lisp's autoload does not call a function when a file is loaded but tells lisp that the function is available and that the given file provides it. Whenever someone calls the (not yet defined) function, the file is loaded.
I think that c-mode is already defined and thus fails to re-register.
Autoload doesn't do what you think it does.
http://www.gnu.org/software/emacs/elisp/html_node/Autoload.html
What you probably want are mode-hooks or eval-after-load.
See eval-after-load vs. mode hook for the difference between the two.
I need CEDET for eassist (eassist-list-methods is quite handy). In eassist.el there's the line
(require 'semantic)
which fails if CEDET isn't loaded. The thing is that I don't need CEDET all the time and it takes a long time to load so I want to defer loading it until I call eassist-list-methods.
Is there a way to run
(load "cedet")
when semantic (or something else that is provided by CEDET) is required?
I'm looking for a simple solution that doesn't change eassist.el.
Genehack is probably right; I'm being too literal in answering the question. The best way to handle something like this is to figure out which function(s) are required by external code, and add autoloads for them.
But if autoload won't work in your case, the normal way to do something when a file is loaded is to do
(eval-after-load "semantic" '(load "cedet"))
But I just noticed that you say that semantic.el fails to load if CEDET hasn't been loaded first. As implied by the name, eval-after-load runs the code after the specified file is loaded.
You can try finding a different file to trigger loading, instead of using semantic.el. (Perhaps some other file that semantic.el requires.)
If necessary, you could hook into require:
(defadvice require (before CEDET-require activate)
(if (eq 'semantic (ad-get-arg 0))
(load "cedet")))
Although (load "cedet") should probably be (require 'cedet), or you'll wind up reloading it every time. (I'm not sure if CEDET has a (provide 'cedet), so I didn't do it that way in my example.)
Note that putting advice on require will not do anything if semantic has already been loaded, so you may need to check (featurep 'semantic) first and load cedet.el immediately if necessary.
Assuming you have all the CEDET stuff in your load-path something like:
(autoload 'eassist-list-methods "cedet" nil t)
in your .emacs.d/init.el (or other init file) should do the trick.
I might be misunderstanding you, but if not the answer is autoload: you want to load eassist.el only when you invoke one of its commands. When it loads it will load semantic or CEDET or whatever it needs -- that's not your problem (it should be taken care of by the design of library eassist.el).
(autoload 'eassist-list-methods "eassist" nil t)