I am trying to write a few keybindings.
M-x describe-function org-todo gives:
...
When called through ELisp, arg is also interpreted in the following way:
`none' -> empty state
""(empty string) -> switch to empty state
`done' -> switch to DONE
`nextset' -> switch to the next set of keywords
`previousset' -> switch to the previous set of keywords
"WAITING" -> switch to the specified keyword, but only if it
really is a member of `org-todo-keywords'.
However, I am trying to use the 'previousset symbol as:
(org-todo 'previousset)
which does not work. I know I am calling it validly because
(org-todo "TODO")
changes it to a TODO.
Where is previousset symbol defined? I can't find a definition anywhere.
ANSWER: I worked out that (org-todo 'left) does what I want. Note that the left symbol is not defined, so it sort of acts as a string instead of a variable, as CantrianBear describes.
One of the comments to following question pretty much answers your question.
previousset as well as nextset lead you to the next set of defined keywords. For that to work, org-todo-keywords needs to contain multiple keywords:
(setq org-todo-keywords '((sequence "TODO" "DONE")
(sequence "TODO2" "DONE2")))
If you just want to cycle through your defined keywords in one sequence, simply type C-c C-t (org-todo).
Related
Very simple question but confuse me for some time:
(setq visible-bell t)
and
(visible-bell t)
both seem work.
But
(desktop-save-mode 1)
works, while
(setq desktop-save-mode 1)
not.
May I ask why is this?
They're different because they're different :)
(setq visible-bell t)
is assigning the value t to a variable named visible-bell.
(visible-bell t)
is calling a function1 named visible-bell (and passing the value t as a parameter).
(Although FYI there is no visible-bell function by default in current versions of Emacs, so it's not obvious to me that this is actually working the way you think? However, assuming for the moment that you do indeed have such a function...)
Emacs Lisp is a 'Lisp-2' meaning it has separate name spaces for variables and functions, and therefore you can -- and commonly do -- have a variable and a function with the same name. Which one is being referred to is always implicit in the context of the code (e.g. setq always refers to a variable).
In short, the two pieces of code are doing very different things. This doesn't mean they couldn't have an equivalent effect (e.g. the function might simply set the value of the variable); but whether or not that's actually the case is entirely up to the definition of the function.
1 In fact the first line of code is also calling a function2: it's calling setq and passing it two parameters visible-bell and t, and setq then sets the value in accordance with its parameters. Hopefully you're now starting to see how lisp syntax works?
2 Strictly speaking, setq is actually a "special form" rather than a function, and special forms are closer to macros than to functions; but these distinctions are not important for this Q&A.
Others have told you the basic points about what setq does and about variables versus functions.
Wrt visible-bell itself:
There is no function visible-bell delivered with Emacs, in any Emacs version I know of, and there never has been. (I've checked back through Emacs 20, and by memory I believe the same was true from the beginning. There is only the variable visible-bell.
So as #phils suggested, is not clear that what you said is true: "both seem to work". Unless some extra code you are loading defines a function of that name (and then there is no way for us to comment on it, not having it to see), evaluating (visible-bell t) raises an undefined (void) function error.
Variable visible-bell is not just a variable. It is a user option, and it has been, again, since at least Emacs 20.
You should not, in general, just use setq to change the value of a user option. In many cases you won't get into trouble if you do that, but sometimes you will, and it is not a good habit to get into.
setq does not perform any special initialization or updating actions that might be appropriate for a given user option. It is not intended for user options. Or rather, user options are not intended for setq - they can be more complex than what setq can offer.
What you should use instead of setq is Customize. Either interactively (M-x customize-option RET visible-bell RET, or C-h v RET visible-bell RET followed by clicking the customize link) or using Lisp code in your init file.
If you use Lisp code then use one of these functions (not setq):
customize-set-variable
customize-set-value
custom-set-variables
Use C-h f followed by each of those function names, to see what (minor) differences there are.
There are 3 issues here.
In Emacs Lisp, the same symbol can be both variable and function.
in the case of desktop-save-mode, it's a function but also a variable.
Because it's a function, so you can call
(desktop-save-mode 1)
Because it's a variable, so you set value to it
(setq desktop-save-mode t)
You can define your own function and also a variable of the same name to test it.
Note: exactly what a function's arguments should be or what the value of a variable makes sense depends on the function or variable.
Now, a second issue. In general, for function (commands) to activate a minor mode, the convention is that a positive integer should mean to turn it on, and otherwise turn off.
Also, for command to activate a minor mode, typically there's a variable of the same name, with value of t or nil, to indicate if the mode is on.
Now, there's third issue. For command to activate the mode, before emacs 24 or so, by convention, if no arg is given, the command toggle current state.
Because all of the above, the issue is confusing. You might see in init things like this:
(desktop-save-mode 1) ; correct. To turn on.
(desktop-save-mode) ; Confusing. Should take value 1 to turn on. Usually works because by default it's off.
(desktop-save-mode t) ; wrong. Take value of positive integer to turn on.
(desktop-save-mode nil) ; Confusing. Value should be integer
(setq desktop-save-mode t) ; wrong. Shoud call function instead
(setq desktop-save-mode nil) ; wrong. Shoud call function instead
(setq desktop-save-mode 1) ; wrong. Shoud call function instead. Besides, only t and nil make sense
So, there's a lot confusion. In emacs 24 (or 23.x), the convention changed so that, if it receives no value, it will turn on, if called in elisp code. (when called interactively as command, it toggles.)
In the end, always call describe-function or describe-variable to read the doc.
Well setq (which is "set" with an auto-quoting feature) is used in assigning a value to a variable. In this example, it's obviously not required because as you mentioned, omitting it works for the first set of examples.
Basically, visible-bell is a variable, and you assign it the value "t" to enable visible bells.
However, desktop-save-mode is an interactive function, so you don't use setq to assign it a value, you call it with parameters.
One good thing to do when you're not sure what something is, is to use the built-in help function:
C-h v visible-bell RET
This will return the information for visible bell -- notice the "v" in the command is because it's a variable. If you wanted to search for information on a function, you would do this:
C-h f desktop-save-mode RET
Incidentally in this case, desktop-save-mode is also a variable, but it's a read-only variable to determine whether or not desktop-save-mode is enabled, so trying to alter it will not work.
I have a function:
(defun alternate-narrow-to-region (start end)
(message "Hi!")
(narrow-to-region start end))
I want all uses of narrow-to-region, except for the one in this function body, to call alternate-narrow-to-region (so narrow-to-defun, narrow-to-page, direct calls to narrow-to-region, end up calling alternate-narrow-to-region).
How do I do this?
To save the original definition (which is in your question title but not in the text), use defalias:
(defalias 'ORIGINAL-narrow-to-region (symbol-function 'narrow-to-region)
"My doc string about this.")
Note that in this case you do not want to use this:
(defalias 'FOREVER-narrow-to-region 'narrow-to-region
"My doc string about this.")
What you want to do is copy the function definition at a given point in time. The latter use of defalias instead has the effect of pointing FOREVER-narrow-to-region to whatever the current definition of narrow-to-region is. If you redefine narrow-to-region then it will point to the new definition, which is presumably not what you want in this case.
As for the question implied by your text, the answer is that you cannot. You cannot get Emacs to always use your function instead of narrow-to-region. This is explained at your other question: code that calls narrow-to-region and is compiled will continue to (in effect) call the original narrow-to-region. (It is not really called at all. Its code is effectively inlined.)
If you wanted to get Emacs to use a replacement command only when called interactively, you could of course remap the original command's key bindings to the replacment. But that does not seem to be the case here.
I am trying to make Tab completion work with RefTeX. When typing C-c [ and selecting the type of reference I have then a prompt in the minibuffer. When I know the beginning of the bib key I want to enter, say for instance Campbell2006, I would like to type Camp Tab and get Campbell2006 [sole completion].
I have managed to set it up for some documents but I do not understand exactly why it works for them and not for others. I have noticed that for the documents that have proper Tab> completion, the following line is added to the file name_of_tex_file.el created in a auto subfolder:
(TeX-add-style-hook "name_of_tex_file"
(lambda ()
(LaTeX-add-bibliographies
"absolute_path_to_bib")))
I think I obtained this results by adding %%% reftex-default-bibliography: absolute_path_to_bib at the end of my files but this is kind of a nuisance, especially when editing the same file on several computers.
Note that RefTeX is working because when I type C-c [ Camp Ret, I get a list (sometime a bit odd) with the Campbell2006 entry.
I have tried to set the %BIBINPUTS% environment variables with no success.
Adding (setq reftex-bibpath-environment-variables '("c:/path_to_bib_file/")) seemed necessary for the C-c [ Camp Ret method to work.
It has somehow the same defects as adding a %%% reftex-default-bibliography: to the end of the file and did not provided the Tab completion.
I have tried various combinations of /, //, \\ and \ as file separators when specifying files but I do not know exact which I should use (I'm using emacs in a windows environment). The issue might be as simple as that but as there are lots of parameters to try I fail do determine where is the problem.
What is the step-by-step method to make RefTeX work smoothly with bibliography, including the Tab completion?
EDIT:
Completion is possible according to the Reftex manual entry about the command reftex-citation:
The regular expression uses an expanded syntax: &&' is interpreted as and. Thus,aaaa&&bbb' matches entries which contain both aaaa' andbbb'. While entering the regexp, completion on knows [sic] citation keys is possible. `=' is a good regular expression to match all entries in all files.
it does not provide precise guidance on how to make it work though.
Kindahero suggests setting a list of the bib entries and use the completing-read command. This sounds sensible, however I would like to generate this list automatically and it seems feasible because it works with some of my documents.
The documentation of reftex-citation is a bit confusing. It promises completion on known citation keys but I believe "known" refers to keys that have been used previously in this session rather than all keys in the appropriate bibliography. You can use the LaTeX-add-all-bibitems-from-bibtex command defined below to load all keys in your bibliography:
(defun get-bibtex-keys (file)
(with-current-buffer (find-file-noselect file)
(mapcar 'car (bibtex-parse-keys))))
(defun LaTeX-add-all-bibitems-from-bibtex ()
(interactive)
(mapc 'LaTeX-add-bibitems
(apply 'append
(mapcar 'get-bibtex-keys (reftex-get-bibfile-list)))))
Suggestions on appropriate hooks to make this happen automatically are welcome.
M-x < TAB > prints all the defined functions.
To check a variable is defined or not evaluating the following expression,
(boundp 'variable-name) C-x C-e will print t if the variable-name is defined else nill.
How to print all the defined variables in emacs.
It's unclear exactly what you want to do with a full list of symbols, since the way in which M-x displays function names is somewhat specialized.
Assuming that you want to programmatically obtain a list of all defined symbols, here's how auto-complete.el does it:
(loop for x being the symbols
if (boundp x)
collect (symbol-name x))
Note that you can also enter M-x describe-var RET, and then press TAB to get a sorted completion list of all symbols.
I presume (apropos-variable "." t) would show you all the variables defined at that point in time.
edit: I presumed wrongly, it would seem.
Interestingly, this actually shows me significantly fewer results than the auto-completions from describe-var.
Can anyone shed light on that?
e.g. the differences between these, when winner-mode has been enabled:
C-uM-x apropos-variable RET winner- RET
C-hv winner- TAB
edit 2: Ah... it looks like apropos may ignore any symbol which lacks a documentation string.
If it's possible, I suggest reassigning the accepted answer.
Extrapolating (heavily!) what is being asked for, here is a way to get a pretty-printed alist of all buffer-local variables with their values. This is very convenient for finding out why for instance a mode isn't behaving the way one expects.
To get this listing, do:
M-x pp-eval-expression RET (buffer-local-variables) RET
Relevant portions from this list can be added almost verbatim to a .dir-locals.el file for use with multiple files.
This is rather queer. I can't set any value to a variable if it is named 's' in an interactive session:
(setq s 'foo)
=> foo
s
=> nil
Why?
Update 1:
Here is the output from describe-variable on s:
s is void as a variable.
Documentation:
Not documented as a variable.
Why is it that s is kept void in emacs lisp as a global variable?
Update 2:
Turned out, it doesn't happen on a vanilla emacs (meaning one of the modules I load in .emacs or some code in .emacs is causing this).
So the question now is:
What would the original source look like when describe-variable yields "<var> is void as a variable"?
I tried it with setq, defconst, defvar, and defcustom, but none of those produced the message I'm showing.
Update 3:
The message shown above is produced when the variable is literally not bound (though it can be fbound).
(describe-variable 'non-existent)
=> "non-existent is void as a variable.
Documentation:
Not documented as a variable."
So latest question is: Is there any way to prevent a certain variable name
from being bound?
An answer to your revised question:
(defvar s)
The only thing is that this won't let you use describe-variable on it interactively.
(You could then do something like (setplist 's '(variable-documentation "Meh")) to set a description for it without going through defvar.
Just bisect your init file (~/.emacs) recursively until you find the sexp that causes the problem. If it is a sexp that loads another library then either don't use that library or fix it by first finding out what its problem is, the same way: bisect the code in that library recursively, etc.
This is a binary search, and it is very quick. You can quickly comment out half, then 3/4, 7/8, etc. of your file, using M-x comment-region (I bind it to C-x ;). with a prefix arg, comment-region uncomments.
With Emacs 23.1, running the following code makes C-h v s RET show “s is void as a variable.”, but I can't reproduce the inconsistency between setq and retrieving the value of the variable (which I agree is weird).
(setq s t)
(make-local-variable 's)
(makunbound 's)
I suspect an Emacs 24-specific feature or bug.