I want to delete a file using racket. I am using following code.
(delete-file c://foo.txt)
I am getting this message.
reference to an identifier before its definition:
c://foo.txt
(delete-file "c:/foo.txt")
BTW, since you're asking very basic questions, perhaps it's better to read the guide first?
Related
I have an org-mode file that I'm trying to export to a Beamer LaTeX PDF through XeTeX. It was working fine last night on this machine, and just as well on another machine on which I edited it afterward. Both are running org-mode 8, Emacs 24, same export process (3 runs of XeLaTeX)
When I synced back to this machine and tried to export again, I got the error Wrong block type at a headline named "". I checked all my headlines and gave them all names, but still got the same result.
Thanks to the wonders of indexed searchable FLOSS code, I immediately found the snippet online:
(env-format
(cond ((member environment '("column" "columns")) nil)
((assoc environment
(append org-beamer-environments-extra
org-beamer-environments-default)))
(t (user-error "Wrong block type at a headline named \"%s\""
raw-title))))
I'm not really solid on elisp at all, though, and I don't know most of what's going on here. From this snippet, what would I do to start debugging? (I realize I can start the emacs debugger, but it's not a PKE meter, I can't just wave it around.)
IMHE the best way to figure out what's wrong when you've found the relevant snippet of code is to use Edebug.
You should read the documentation to learn more about it, but basically here is my procedure:
identify the part of the code that crashes
instrument the code with Edebug (C-uC-M-x)
re-execute the code and go step by step to figure out what's going on (n)
If the problem is in another function, jump to it GOTO 2.
Iterate until you've understood the code and find a way to fix it.
Posting this answer just so that the specific solution to the particular problem the error was flagging is understood.
Apparently the version of Beamer I have on the other machine has a "normal" Beamer environment that specifies an otherwise blank, unformatted block. This is not present in this machine's install, or at least org/XeLaTeX don't know about it.
My steps were:
Search for all unnamed headings
Name each of them uniquely
Reproduce the error with the identifying string
Check the block type property against the available type list given in org-beamer-mode
Remove the offending type and replace it with another one
This is great and all, but I don't think it's the "best answer" because it involves no actual understanding of what the emacs interpreter was trying to tell me. If I didn't have a good idea of what was going on generally with the TeX, there's no way it would have worked. Dunno if this technique would impress anybody at an interview ;)
I was looking for a method to show a list of filenames in a directory, and then select one of them.
I found this:
https://github.com/lawlist/dired-read-file-name and it seemed promising, so I copied it to my emacs direcory and tried:
(require 'dired-read-file-name)
but I get error
error: Required feature `dired-read-file-name' was not provided
require is not going to work because the source of dired-read-file-name.el does not have a provides expression. You might want to add:
(provide 'dired-read-file-name)
add the end of the file.
Alternatively, you can just load or more low-level load-file.
Also have a look at this.
I found that font-lock-add-keywords is the key but I cannot find how to add a pattern. For example, in clojure;
(defn a-function-name [argument vector]
...)
a-function-name is highlighted becuase it's after defn and before [argument vector]. How can I write a rule for this?
(font-lock-add-keywords 'lisp-mode XXXXX)
I cannot write XXXXX part for myself.
=======================
Thank you to all of you :-) Yes, I can find clue in docs and clojure-mode.el as of you said.
Here is what I do and it works well (at least for me)
(font-lock-add-keywords
'lisp-mode
'(("(\\(#defn\\)\\>[ \r\t\n]*\\(\\sw+\\)+\\>?"
(2 'font-lock-function-name-face))))
Why I need this is that I define some macros and emacs does not highlight them properly.
Type C-h f font-lock-add-keywords. In the help for that function, there will be a link for font-lock-keywords, where the format for what you call XXXXXX is described.
If with that help you are still having trouble, post your attempt to achieve what you want so you can receive more specific help regarding your problem.
To add to what #juanleon said: See the Elisp manual, node Search-Based Fontification for information about font-lock-keywords. That will help you "write the XXXXX part for yourself."
Then, as #juanleon said, try something and ask for more help here if it doesn't work. Code tried gets help.
For example, standard libraries in C/C++ are used very often, and it's very inefficient to go to the web browser, search for the code example how to use a library component, copy the source code and modify to suit your need; a few month later, you need to use that library component again but forgot how to use it, and you have to repeat the whole process again!
This process is not very productive for me because after we learn something the first time, we do not need to fully study the same thing again; just part of it can help us recall how to use it. I want my written code or example code copied from the web site to be stored for later reference and modification.
Emacs macro is an option, but I think you have to type the whole source code to make a desired template. What if I found a well written code, and I want to store that code segment for future reference? Macro won't be productive because I have to type the whole thing.
Is there Emacs plugin for doing this?
I wouldn't recommend snippets for the task that you described.
Snippets are meant to be repeated often. You can't have a lot of them.
What you need is something that you use rarely, but can have a lot of.
I'm using org-mode for this task. With org-mode you can:
Organize your knowledge by language/library etc.
Include small code snippets directly via babel.
Attach any number of files to any heading.
This way you get the overview/description via the headings,
and the actual code via code blocks / attachments.
Another advantage is that you can easily grep your org-file / your attachments.
Other advantages are timestamps, TODOs and all kinds of export that org-mode provides.
UPD
Just to give you a sample of what it can do (open in in emacs, otherwise it looks ugly):
https://gist.github.com/abo-abo/6040382/raw/1be55e30a9ed8d81cc1b2b752b7d498d05e72978/hyper.org
There is quite a list on the EmacsWiki: Templates.
Personally I know TempoMode and Yasnippets. I prefer Yasnippets. The snippets are very easy to write and have support for variable fields which you enter on snippet insertion.
This should provide a command inserting the last item of current kill-ring.
(defun my-code ()
(interactive "*")
(insert "(defun ")
(save-excursion (insert (concat "()
(interactive \"*\")
(insert \"" (car kill-ring) "\"))"))))
Remains to specify the name of the command when done - and installing it.
In the past I have used Else-Mode to do just that sort of thing, especially when the project I was working on had a very rigid and long, required function header comments.
You can look to SRecode from CEDET package. Besides standard templates, like yasnippet, etc., it also provides support for content-aware templating, like some templates could be expanded only inside the classes, some only as top-level declaration, etc.
I wrote a Lisp function earlier that had an error. The first challenge was to figure out how to view the function again. That challenge is solved. Now that I see WHAT I have done wrong, I want to modify the contents of the defined function without rewriting the whole thing?
Seems like as intelligent as Lisp is, there HAS to be a way to do this, I just don't know what it is because I am fairly new to the language. Can this be done?
Judging from the question, I think that you have a strange setup. It seems to indicate that you are writing your functions directly at the REPL. Don't do that.
The usual setup is to have an IDE (for example, Emacs with Slime) where you edit a source file, and then "send" top-level forms (like function definitions) to the REPL.
Every useful REPL has a history functionality. It allows you to move in the history of your input backwards and forwards.
When I write code in the REPL simple keystrokes like m-p gets back earlier code. Some IDEs might even be able to locate source code in a Lisp listener with m-. .
In most REPLS you can also search incrementally backwards.
If you want a log of your input use the function DRIBBLE..
There are some more options, like retrieving the code from the function - when a Lisp IDE supports that.
There is the advice functionality in many Lisps, which lets you run additional code before or after or around an existing function. But the comment is right, why wouldn't you rewrite a function if you're still learning and trying things out? Do they charge you by the compile cycle?