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#+TITLE: Emacs Lesson 1
#+AUTHOR: Arne Brasseur
#+STARTUP: showall

* Keybindings Cheatsheet

| | Getting out | |
|------------+--------------------------------------------------------+----------------------------------|
| C-x C-c | Exit emacs | save-buffers-kill-terminal |
| C-g | Cancel running or partially typed command | keyboard-quit |
| q | Close window (in read only buffers) | quit-window |
|------------+--------------------------------------------------------+----------------------------------|
| | Working with files | |
|------------+--------------------------------------------------------+----------------------------------|
| C-x C-f | find (open) file | find-file |
| C-x k | kill (close) buffer | kill-buffer |
| C-x C-s | Save | save-buffer |
| C-x s | Save All | save-some-buffers |
|------------+--------------------------------------------------------+----------------------------------|
| | Working with windows | |
|------------+--------------------------------------------------------+----------------------------------|
| C-x 0 | Minimize window | delete-window |
| C-x 1 | Maximize window | delete-other-window |
| C-x 2 | Split window horizontally | split-window-below |
| C-x 3 | Split window vertically | |
| C-x o | Go to other window | other-window |
| C-x b | Switch to specific buffer | ido-switch-buffer |
| C-x C-b | List all buffers | list-buffers |
| S-<arrows> | Move around multiple windows | |
|------------+--------------------------------------------------------+----------------------------------|
| | Getting help | |
|------------+--------------------------------------------------------+----------------------------------|
| C-h k | Describe key | describe-key |
| C-h f | Describe function/command | describe-function |
| C-h t | Open tutorial | help-with-tutorial |
| C-h K | Show manual for key command | Info-goto-emacs-key-command-node |
| C-h m | Describe current major and minor modes | |
|------------+--------------------------------------------------------+----------------------------------|
| | Copy paste | |
|------------+--------------------------------------------------------+----------------------------------|
| C-SPC | "start selecting text" | set-mark-command |
| C-w | "Cut" | kill-region |
| M-w | "Copy" | kill-ring-save |
| C-y | "Paste" (yank) | yank |
| | "Paste previous ones" (cycle) | yank-pop |
| C-k | "Cut till end of line" (repeat to kill mutliple lines) | kill-line |
|------------+--------------------------------------------------------+----------------------------------|
| | Working with Lisps | |
|------------+--------------------------------------------------------+----------------------------------|
| C-x C-e | Evaluate previous expression | eval-last-sexp |
| C-M-x | Evaluate outer expression | |
|------------+--------------------------------------------------------+----------------------------------|
| | Clojure | |
|------------+--------------------------------------------------------+----------------------------------|
| C-c M-j | Start a REPL in the current project | cider-jack-in |
| C-c M-n | Switch to current namespace | cider-repl-set-ns |
| C-c M-c | Connect to a REPL already running in a terminal | cider-connect |
| | Stop the REPL | cider-quit |

* Theory
** Emacs
*** Function, Commands, Key bindings


Emacs is essentially a virtual machine that runs Lisp code. The editor functionality is written in Lisp,
and other "apps" can be created that run on the Emacs platform. (Try =M-x tetris= or =M-x doctor=). This
is why Emacs is praised for its extensibility, you can program the editor itself from within the editor.

To do so you define functions. Functions that are meant to be executed by the user are called commands,
they have to have =(interaction)= as the first expression within the function body.

You can try this in the *scratch* buffer that Emacs starts with.

#+BEGIN_SRC emacs-lisp
(defun go-down-five-lines ()
(interactive)
(forward-line 5))
#+END_SRC

Put your cursor after the last closing parantheses and type =C-x C-e=. Now you've executed the function
definition, meaning the function (command) is now defined. You can execute it with =M-x go-down-five-lines=.

To be more useful we can bind it to a key.

#+BEGIN_SRC emacs-lisp
(global-set-key (kbd "<f9>") 'go-down-five-lines)
#+END_SRC

Is this case we set a global key binding, so we can use the key to invoke the command from anywhere in Emacs.
Some bindings are specific to a certain context, some commands might only be active when editing Lisp files,
or Ruby files, or when viewing the contents of directories.

*** Help

Emacs has various help systems built-in, you should be able to learn everything about Emacs from within
Emacs. All these help commands are bound to key combinations starting with =C-h=, for example, =C-h f= will
prompt for a function. You can find out what it does, and what key, if any, it is bound to. Other notable
help commands are

| C-h ? | List all help commands | help-for-help |
| C-h k | Describe key | describe-key |
| C-h K | Show manual for key | Info-goto-emacs-key-command-node |
| C-h i | Open the Emacs manual | info |
| C-h t | Open the (pretty old school) tutorial | help-with-tutorial |

Exercises

- What does the command =zap-to-char= do?
- What key is it bound to?
- Try using it
- What command is bound to the key =M-SPC=? (meta-space)
- What does it do?
- Jump to its description in the manual.
- Try using it
- In the cheat sheet at the top some keybindings or command names are missing, look them and fill them in

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