Emacs Lisp: How to, an interactive buffer with REPL? - emacs

Imagine the dunnet.el game, the eliza doctor or the IELM mode...; This is, evaluating answers and prompting new questions on the main buffer, then making some actions according to their elisp rules.
I would to create something like an interactive assistant, BUT NOT prompting from minibuffer as (interactive) does (not doing M-x)... I need a kind of REPL loop. So the question i how to get interaction on the working buffer (the main screen), like any text conversational/adventure, but for call my defun'ed functions on this way.
So i need a basic elisp skeleton, to make a custom REPL. The target is to make an assistant with a natural language, then parsing the anwsers, and making some actions according the rules.
Thank you for your time,
Steve,

Check out ielm, which is an elisp repl included with emacs.

Depending on what can go on in your buffer, can you just give it a major mode with an appropriate re-binding of return? (This answer vaguely inspired by Lisp-Interaction-Mode's C-j)

You should bind all keys that use for moving in buffer like C-p C-n, Up Down Arrows/ page up/down just bind them to (lambda ()). change function for C-b and C-f (Left Right Arrows) if cursor position is in beginning or end of the line. And bind Return key to function that read current line from end to optional prompt (you can use Regex to remove the prompt) do whatever you want with that string, and then go to the next line in the buffer and print your result.

Related

Emacs Macro to Start in Shell Mode and Run a Command

I have a confession: I don't know Lisp. Despite that fact, with a bit of help from some co-workers, I managed to write an emacs macro/script which:
switched to shell mode (ie. M-x shell-mode)
disabled truncating lines (ie. M-x toggle-truncate-lines)
started a database console (ie. "mysql")
I was then able to start emacs with that macro using the --script option, and suddenly I had a way to start mysql in a much friendlier environment with a single command :-)
But here's the problem: I changed jobs and left that script behind. Now I'd very much like to re-create that script at my new job, but I no longer have any emacs experts to help me write it like I did at the old job.
Now, I really hate SO posts where someone basically says "please write my code for me", so I don't want to do that. However, if any emacs macro experts could at least give me some pointers (like "here's how you invoke a M-x command in a macro"), or point me to an emacs-macro-writing guide, or otherwise "teach me to fish" on this issue, I would greatly appreciate it.
... and if someone just happened to have a similar script already lying around that they wanted to post, I certainly wouldn't complain ;-)
Most emacs commands (i.e., M-x toggle-truncate-lines) can be translated directly to elisp by wrapping them in parentheses:
(toggle-truncate-lines)
The rumours are true, in lisp you just scatter parentheses around and they make magic.
Now in this case, you can do better. Toggling makes sense for an interactive function, but in a program you don't really want to toggle truncate-lines, you want to turn on truncate-lines. Its the same thing if truncate-lines was turned off to begin with, but you don't know when your program will be run next. Anyways, in Emacs, features are often controlled by a variable. In this case, the variable is truncate-lines, and to turn that feature on, you set the variable to t (which means true).
To do this, use:
(setq truncate-lines t)
We use setq instead of = for assignment, because they made lisp before = had been invented.
For the real scoop you should take a look at Robert Chassel's excellent "An introduction to to Programming in Emacs Lisp". It comes built-in with your emacs, you can get to it with C-h i m Emacs Lisp Intro.
A good way (I think) to start writing elisp functions is to record keyboard macros, and then to analyse them using edit-kbd-macro
For example, if you start recording a keyboard macro using f3, then do interactively all the things you want and terminate the macro using f4, you can see the underlying emacs-lisp commands using M-xedit-kbd-macrof4 (this last f4 is the key binding you'd have used to execute the keyboard macro)
<<shell>> ;; shell
<<toggle-truncate-lines>> ;; toggle-truncate-lines
mysql ;; self-insert-command * 5
RET ;; comint-send-input
Now you can write a script using these functions, looking up the documentation (e.g. C-h ftoggle-truncate-lines) to see if you should call them with special arguments in non-interactive mode.
You should also replace self-insert-command by calls to insert.
This should give you something like the following script, which you can call using emacs --load myscript.el
(shell)
(toggle-truncate-lines 1)
(insert "mysql")
(comint-send-input)
Of course, this might not work as expected the first time, so you might have to eval (setq debug-on-error t) to get debugging information.
What version of Emacs are you using?
In Emacs 24, I have M-x sql-mysql, which does everything you ask and has font-locking.

How do I determine why emacs indented a certain amount?

In Emacs I'm editing some source code, and I hit <tab>. Emacs indents the line to n spaces. I'd like to change the amount that indents for that kind of line. How do I figure out what rule emacs applied to indent that line by n spaces?
I want to change n, but I need to figure out which of the many indentation-related variables Emacs just used.
A generic answer is difficult. Some modes will make this more apparent than others, but in the general case (as they are free to implement indentation however they wish) I don't think you'll get away from needing to read some elisp.
Starting with the binding for TAB will work, but might be slightly time-consuming depending on how many layers of indirection are involved.
If you know that the major mode in question implements its own indentation, then one (non-rigorous, but fast) approach that you could try to help track down the functions being called is to use ELP, the built in elisp profiler. elp-instrument-package will instrument for profiling all functions with names matching the prefix string argument you specify. Therefore you might do something like the following in a PHP file (noting that php-mode tells you that it is derived from c-mode)
M-x elp-instrument-package RET php- RET
M-x elp-instrument-package RET c- RET
M-x elp-instrument-package RET indent RET
Now type TAB in your source code, and run M-x elp-results to see which of those instrumented functions were called.
At this point you're on your own -- look for the likely suspects, and see what the code is doing -- but it can be a handy way to filter the search.
Once you've finished, use M-x elp-restore-all to prevent any further profiling.
If you're using a mode based on cc-mode (e.g. c-mode, c++-mode, java-mode, etc.), you can hit C-c C-s and it'll tell you what syntactic category the line is. If you want to change it, hit C-c C-o and you'll be guided through the process. Check out the cc-mode docs on customization for more details: https://www.gnu.org/s/emacs/manual/html_node/ccmode/Customizing-Indentation.html
If you happen to enjoy getting your hands really dirty, there's always the elisp debugger to tell you just what Emacs is up to.
If you hit C-h k TAB you'll find the function that Emacs is running (e.g. indent-for-tab-command) then you can do M-x debug-on-entry RET indent-for-tab-command RET. Now whenever you hit TAB you'll pop up a debugger and can watch the execution step by step.
Depending on your taste for debugging, it's either a maddening or enlightening experience. Either way, don't forget to M-x cancel-debug-on-entry when you're done.

Simple Emacs keybindings

I have two operations that I do all the time in Emacs:
Create a new buffer and paste the clipboard. C-S-n
Close the current buffer. C-S-w
Switch to the last viewed buffer. C-TAB
I feel like a keyboard acrobat when doing the first two operations. I think it would be worth trying some custom key bindings and macros.
A few questions about this customization:
How would I make a macro for #1?
Are these good key bindings? (I know this is a bit subjective, but they might be used by something popular that I don't use.)
Has anyone found a C-TAB macro that will act like Alt+Tab in Linux/Windows? Specifically, I want to have a stack of buffers according to the last viewed timestamp (most recent on top). I want to continue cycling through the stack until I let go of the Ctrl key. When the Ctrl key is released, I want the current buffer to get an updated position on the stack.
Have you tried using vertically or horizontally split windows for this (via C-x 3 or C-x 2)? It seems like it would give you fewer steps - even if you implement something like you're talking about.
I find split windows really speed up copy and pasting operations. I use the arrow keys on my num pad to switch among windows (windmove-left/-right/-up/-down), so it's only one key to press and you go to the window you want.
I guess this is a little different from what you're asking for, but it sounds like it might help speed things along a bit.
C-x left and C-x right cycle through buffers, but you have to hit it multiple times, you can't just keep the key pressed down.
For creating a macro for #1, you just start a macro, hit the keys you usually do to create a new buffer, and stop the macro.
So it would be something like:
C-x ( C-x b NEW RET C-x )
You can then save NEW to a file once you're done pasting, so you can use the macro again to create a new buffer. C-x e to try out the macro. If it works you can save it into your init.el file. This is done with:
M-x name-last-kbd-macro
Then you'll get a prompt to enter the name of your choice. This is only good for the current session. Then you save the named macro to your initialization file. First you open your .emacs or init.el file. Then you place point where you want the macro definition to go, then you type:
M-x insert-kbd-macro
Now you can run your macro using its name via M-x <macroname> . You can bind your macro to keys too (in your .emacs or init.el file):
(global-set-key (kbd "C-c a") '<macroname>)
For example this is how your init.el would look after creating a macro that opens a new buffer called NEW that is not associated with a file and binding this macro to C-c n:
;; Creates a new unassociated buffer called NEW
(fset 'new-buffer "\C-xbNEW\C-m");
;; Shortcut for new-buffer
(global-set-key (kbd "C-c n") 'new-buffer)
You can also throw in the paste, buffer close, and buffer switching operations. I guess you'd have to save the buffer to a file manually.
Some resources
Information about macros on EmacsWiki
Possibly useful: Swap text between buffers
start by invoking start-kbd-macro, finish by with end-kbd-macro. Afterwards you may immediately test the new macro with call-last-kbd-macro. If you're happy with the result you might want to save the macro.
Emacs generally doesn't use C-S keybindings and they are easy to use, so I'd call them good. They might cause problems if you're using the terminal version of Emacs, but I assume that's not the case with you.
I use this simple snippet:
(global-set-key (kbd "<C-tab>") 'bury-buffer)
bury-buffer basically makes the current buffer the last in the buffer-list so you'll be able to cycle buffers in a predictable order.
I wouldn't make a macro for that but write a function like someone else posted on this page. Instead of (cua-paste nil) you could also use (yank). I'm not sure which one's better and why.
I don't like them that much. For things that I use often I'd like to do as little finger acrobatics as possible, so that would mean modifier+key instead of modifier1+modifier2+key.. or use a function key if you don't feel tied to the homerow.
no comment

Does Emacs has word and line completion (like Vim's insert mode completion)?

Vim completes words and lines with CTRL-X P and CTRL-L. There's a Emacs plugin called Company mode but this plugin interfere and cause conflicts with lots of things within Emacs (with global linum and yasnippets). I know that I can complete words with CTRL-/ in Emacs. But it is possible to take previously written lines to complete code?
Maybe you're looking for hippie-expand? From that web page (as of this writing, anyway):
HippieExpand looks at the word before
point and tries to expand it in
various ways including expanding from
a fixed list (like expand-abbrev),
expanding from matching text found in
a buffer (like dabbrev-expand) or
expanding in ways defined by your own
functions. Which of these it tries and
in what order is controlled by a
configurable list of functions.
For a comprehensive list of completion options visit the emacs wiki page on completion.
There are a gazillion ways to do completion in Emacs. Some are mode specific, some inline, some configurable and what not. Here is a list of modes that might help you.
Use numberic argument to complete by line, say M-5 M-/ will complete by line, while M-/ alone still complete the normal way.
hippe-expend function has a very useful feature which is :
With a positive numeric argument, jumps directly to the ARG next function in this list. With a negative argument or just C-u, undoes the expansion.
Customize the expansion functions in hippie-expand-try-functions-list and put the function try-expand-line as 5th list element, then you could use M-5 M-/ to complete by line.
This tip is very handy and useful and I highly recommend it.
Also worth noting: if your window manager does not steal Alt-tab, emacs will auto-complete with Alt-tab (I set up my window manager to user the "windows key" instead of alt for this very reason).
If you are using evil, this is the most vim-like solution I use:
(defun my-expand-lines ()
(interactive)
(let ((hippie-expand-try-functions-list
'(try-expand-line-all-buffers)))
(call-interactively 'hippie-expand)))
(define-key evil-insert-state-map (kbd "C-x C-l") 'my-expand-lines)
This way you can use our old friend C-x C-l in insert mode for whole line all buffers completion.
Thanks #ymln for the suggestion of using try-expand-line-all-buffers.

In emacs how does the "hyperlink" in the *Help* buffer work?

I'm trying to figure out how the "hyperlink" works in the *Help* buffer (so that I can implement something similar in the output of M-x compile). Here is a more detailed description of the behaviour I want to imitate:
M-x describe-function find-file opens up a *Help* buffer. The first line of this buffer (for me) shows: find-file is an interactive Lisp function in files.el. files.el is underlined and clicking (or hitting enter when point is there) opens a new buffer with files.el and the point positioned at the definition of find-file. Doing a describe-key for says invokes push-button in button.el, which tells me Perform the action specified by a button at location pos - but how do I define a button and associate an action with that button in my own buffer?
The major mode of the *Help* buffers is help-mode. In its source code (help-mode.el), you find function help-make-xrefs that "Parse[s] and hyperlink[s] documentation cross-references in the given BUFFER". You may check it how it was implemented.
Otherwise, I'd suggest using org-mode instead, which uses the simple form [[URI][caption]] to mark hyperlinks.