Elisp

Yayu Wang included in category Emacs

2022-03-31 2025-03-19 1324 words 6 minutes

string

concat

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(setq str1 "Hello, ")
(setq str2 "world!")

(setq result (concat str1 str2))

loop

for

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(dotimes (i 5)
  (message "Iteration %d" i))
;; Iteration 0
;; Iteration 1
;; Iteration 2
;; Iteration 3
;; Iteration 4

(dolist (item '(1 2 3 4 5))
  (message "Item: %d" item))

;; Item: 1
;; Item: 2
;; Item: 3
;; Item: 4
;; Item: 5

equal

eq

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(eq 'foo 'foo)
;  ⇒ t


(eq ?A ?A)
;; ⇒ t


(eq 3.0 3.0)
;; ⇒ nil
;; Equal floats may or may not be the same object.

(eq "asdf" "asdf")
;; ⇒ nil

(eq [(1 2) 3] [(1 2) 3])
;; ⇒ nil

(eq (point-marker) (point-marker))
;; ⇒ nil

equal

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(equal "asdf" "asdf")
;; ⇒ t


(equal [(1 2) 3] [(1 2) 3])
;; ⇒ t


(equal (point-marker) (point-marker))
;; ⇒ t

list

add-to-list

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(setq my-list '(1 2 3))
(add-to-list 'my-list 4)
;; Result: my-list is now (1 2 3 4)
(add-to-list 'my-list 2)
;; Result: my-list remains (1 2 3 4) since 2 is already in the list

remove from list

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(setq my-list '(1 2 3 2 4))
(setq my-list (remove 2 my-list))
;; Result: my-list is now (1 3 4) since all occurrences of 2 are removed

switch

pcase

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(pcase system-type
  ;; GNU/Linux or WSL
  (gnu/linux
   (message "This is GNU/Linux"))

  ;; macOS
  (darwin
   (message "This is macOS"))

  ;; Windows
  (windows-nt
   (message "This is Windows"))

  ;; BSDs
  (berkeley-unix
    (message "This is a BSD"))

  ;; Other operating system
  (_
   (message "Unknown operating system")))

regex

match

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(let ((text "Hello, my email is user@example.com ????"))
  (if (string-match "\\(user@example.com\\)" text)
      (message "Found email address: %s" (match-string 1 text))
    (message "Email address not found")))

non-greedy

use ?

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(let ((text "This is a test <foo>bar</foo> test"))
  (if (string-match "<.*?>" text)
      (message "Greedy match: %s" (match-string 0 text))
    (message "No match")))

defun

defun define function

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(defun function-name (args)
(interactive "...")
...
)

interactive code: reference

interactive

通过 interactive 可以把一个函数变成一个可交互的命令
interactive 的命令才可以通过 M-x 执行, 类似把这个函数对用户 public

file

get parent directory

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(file-name-directory buffer-file-name)

file name without suffix

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(file-name-sans-extension (buffer-name))

lexical-binding

with ;; -*- lexical-binding: t -*- in the first line, emacs use lexical scope

Binding

A binding is a correspondence between a name and its value.

In Lisp you can create a binding using ‘let’

a binding made by ‘let’ lasts until the end of the ‘let’ form.

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  (let ((a 1))
    (let ((a 2))
      (let ((a 3))
        (print a))
      (print a))
    (print a))
  ;; ==> 3
  ;;     2
  ;;     1

Dynamic Binding Vs Lexical Binding

Lexical and dynamic binding refer to how variables are looked up by their names.
Two regimes for handling variable binding emerged:
dynamic
- All variable names and their values live in one global table.
lexical
- Each binding scope (function, let syntax, …) creates a new table of variable names and values, organised in a hierarchy called “the environment”.

mode

major mode

get major mode

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major-mode

org-mode

get major mode keymap

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(current-local-map)

keymap

create keymap

(make-keymap) full keymap with nil binding
(make-sparse-keymap) empty keymap

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  (let ((keymap (make-keymap))
        (sparse-keymap (make-sparse-keymap))))

suppress-keymap

changes the contents of the full keymap keymap by remapping self-insert-command to the command undefined

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(let ((map (make-sparse-keymap)))
  (suppress-keymap map)
  (keymap-set map "q" 'quit-window)
  map)

unbind key

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(define-key 'keymap key-sequence nil)

(unbind-key key 'keymap)

Quoting

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(quote (+ 1 2))
;;     ⇒ (+ 1 2)

(quote foo)
;;     ⇒ foo

'foo
;;     ⇒ foo

'(quote foo)
;;     ⇒ 'foo

['foo]
;;     ⇒ ['foo]

Backquote

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`(a list of (+ 2 3) elements)
;;     ⇒ (a list of (+ 2 3) elements)

`(a list of ,(+ 2 3) elements)
;;     ⇒ (a list of 5 elements)

(setq list '(hack foo bar)) ;;     ⇒ (hack foo bar)
`(use the words ,@(cdr list) as elements)
;;     ⇒ (use the words foo bar as elements)

priority

overriding-terminal-local-map
overriding-local-map
text property 'keymap
emulation-mode-map-alists
minor-mode-overriding-map-alist
minor-mode-map-alist (Minor Mode)
text property 'local-map
(current-local-map) (Major Mode)
(current-global-map) (Global Map)

minor-mode

check if active

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(bound-and-true-p which-key-mode)

list

range

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(number-sequence ?a ?z)

in list

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(member 1 (number-sequence 2 3))

loop

dotimes

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(dotimes (it 10)
  (message "%s" it))

dolist

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(dolist (elem (number-sequence 0 10))
  (print elem))

hash

put

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(puthash key val hash-table)

hotkeys

Keymap	Function
C-M-f	forward-sexp (coresponding bracket)
C-M-b	backward-sexp (coresponding bracket)

org-mode

Keymap	Function
C-c -	add - ahead of current line

buffer & window

get

可以通过 (get-buffer BUFFER_NAME) / (get-buffer-window 直接拿到 buffer / window
可以不存在的话是 nil

switch

window 的话可以用 ace-window 的 aw-switch-to-window WINDOW_NAME

function

function	key	functionality
file-exists-p	nil	file exisit
file-name-directory	nil	get the directory of a file
buffer-file-name	nil	current buffer/file name
backward-up-list	C-M-u	upper level element (method -> class)

GPG

keeping your secrets encrypted on your file system is an easy way of keeping your secrets secret

Gpg(GNU Privacy Guard) is natively supported in emacs called EasyPG
只用一个gpg key管理所有加密文件和链接
可以不用每次输密码获取 root 权限

authinfo

auth-sources 变量指定 authinfo 文件
格式 machine <HOST> login <ACCOUNT> port <PORT> password <PASSWORD>
- example machine localhost login root port sudo password rootpasswd123
shell access gpg2 -q --for-your-eyes-only --no-tty -d ~/.authinfo.gpg | sed -n 's,^machine gmail.com .*password \([^ ]*\).*,\1,p'

Creating a key

gpg --gen-key

cache password

font

describe char

display current char info

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C-u C-x =

align

第一次知道 C-u M-x 调用的命令跟直接 M-x 调用的还是不一样的
C-u M-x align-regexp 使用的是更高级的 align-regexp
- regexp: match the place you are interested in aligning; to do it, one of its parenthesis groups will be extended with spaces, or shortened by deleting characters
- parenthesis group: choose which one
- spacing: if the group is shorter than this, spaces will be added to it; if it's longer, characters will be deleted from it, starting at the end (unless it's longer for the purposes of alignment, of course)
- repeat: well, this is obvious, I think
- justify: non-blank characters inside the group won't be deleted, and necessary spaces will be added/deleted from the left. On your second case, try: regexp \([0-9]+\), group -1.
- column (instead of spacing): align to that fixed column (of course, it doesn't work well with “repeat”).

debug

debug function

M-x debug-on-entry 设置入口
直接运行函数
cancel-debug-on-entry

keymap

Shortcut	Function
d	step through
c	continue(step out)

on error

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(setq debug-on-error t)

bugs

poll freeze

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in poll () at /usr/lib/libc.so.6

disable XIM (maybe) ref: https://gitlab.freedesktop.org/xorg/lib/libx11/-/issues/35

search by value

apropos-value

package

unload

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(unload-feature 'miao)