技术笔记

When new programming languages appear, a major mode for Emacs that does basic syntax highlighting and indenta- tion appears almost immediately. But i think auto format is more important, no matter what indent you write, code always tobe same format, that means you don't need care about indent at all.

TAB: Indenting the Current Line

Disabling tab characters

If you dislike the use of tab characters and if you prefer whitespace, customize the variable indent-tabs-mode.

Changing the amount of indentation

The variable tab-width controls how many characters of spacing each tab uses. It also controls the amount of whitespace to use if you disabled indent-tabs-mode.

Indenting Regions

In an ideal world, pressing TAB with an active region is all you need to re-indent it. Unfortunately, Emacs might not support that, or in some programming languages it is not physically possible to determine the correct indentation. Pressing TAB follows most of the same rules as line indentation: Emacs attempts to indent according to the indent-line-function and it falls back on simply inserting TAB characters (or whitespace, if you disabled indent-tabs-mode).

Typing C-M- explicitly indents the region; for some modes it works identically to TAB and in others it doesn’t. If you give the command a numeric argument, it will indent the region to that column (i.e., the number of characters) and Emacs will also use your fill prefix (if you have one) and fill the text accordingly. C-M- is occasionally useful as it respects your fill prefix. However, if you want to indent a fixed number of columns, you should use C-x TAB.

C-x TAB explicitly indents the region a certain number of columns. It also takes negative and numeric arguments. However, if you don’t pass an argument, Emacs will en- ter an arrow-key-driven indentation mode that lets you interactively indent the region with S-<left> and S-<right>.

There are several built-in tools – and just as many third-party ones – in Emacs that expand text. All of them serve a slightly different purpose, but the goal is to minimize typing and maximize automation.

• Abbrev
• DAbbrev
• Hippie expand
• Skeletons
• Tempo
• YASnippet
• Autoinsert

Abbrev

DAbbrev and Hippie Expand

DAbbrev is not smart. It looks at other words in your buffer and it attempts to complete the word at the point to one of those. That does not make it useless – it is still useful – it’s just that Hippie Expand is so much better.

To use Hippie Expand effectively, you should replace DAb- brev as the two – though it’s possible to use both – really don’t complement one another at all. Add this to your init file to switch to Hippie Expand:

(global-set-key [remap dabbrev-expand] 'hippie-expand)

Hippie Expand expands more than just words. The variable hippie-expand-try-functions-list is an ordered list of expan- sion functions Hippie Expand will call with the text at the point when you call M-/.

What I like most about Hippie Expand is the file name com- pletion. It works exactly like your shell’s TAB-completion: you type M-/ and Hippie Expand will try to complete the filename or directory at the point. If you ever find yourself inserting absolute paths or relative file names in code, config- uration files or documentation — Hippie Expand will make your life much easier.

Another great feature is its ability to complete whole lines. It will fall back to word completion if it runs out of ideas, and if you regularly write elisp, then Hippie Expand will guess if the text at the point is a potential elisp symbol and automatically complete it for you also.

Keyboard Macros

You can record keystrokes and commands in Emacs and save them for later playback as a keyboard macro. A keyboard macro in Emacs is very different from a lisp macro and you should not confuse the two.

Basic Commands

You can also pass the universal argument and digit arguments to the macro commands:

Appending to the last macro (C-u F3) is occasionally useful, but passing a numeric argument to F4 is very useful since replaying the macro a set number of times is a frequent thing indeed; so much so that passing digit 0 (C-0 F4 or C-u 0 F4, for instance) will run the macro over and over again until it terminates with an error, such as reaching the end of a buffer or when a command in the macro triggers an error.

Advanced Commands

There is an entire prefix key group, C-x C-k, dedicated to Emacs’s macro functionality. There are many commands and you are unlikely to ever use most of them.

Interactive Macro Playback

Let’s start out with the counters. When you start recording, Emacs will automatically initialize an internal counter to zero, and every time you press F3 during the recording, Emacs will insert the counter and then increment the internal counter by 1. There are, of course, many creative uses for the counter: creating numbered lists is the most obvious.

The standout command is C-x C-k q. When you call it, Emacs will tag that step in the macro recording and ask the user for advice – in effect stopping the macro temporarily to prompt the user – before continuing.

Saving and Recalling

Macros in Emacs are stored in a macro ring, a concept that you should recognize from other parts of Emacs (like the kill ring and undo ring.) Creating a new macro automatically stores old macros in the macro ring without you having to do anything. The commands below let you save and recall from the macro ring, edit and bind macros to keys, and more.

Text manialations is one aspect Emacs is especially good at, and it has a variety of tools to help you. Massaging text files for further processing or extracting pertinent information from log files are both common things to do in Emacs.

Editable Occur

I introduced M-x occur in Occur(M-s o in helm): Print lines matching an expression as a way of collating all lines that match a certain pattern.

You can typing e begin to edit, and after you finish, C-c C-c to commit the changes to their original lines, it is especially great for keyboard macros and search & replace.

Deleting Duplicates

By default, M-x delete-duplicate-lines deletes the first dupli- cate line it encounters, starting from the top. With a single universal argument, it starts from the bottom and therefore deletes the last.

Flushing and Keeping Lines

Sometimes you want to filter lines in a region by a pattern; whether that is to flush lines that match a pattern, or keep the ones that do.

Both commands act on the active region so it is common – if you want to do this on a whole buffer - to call C-x h to select the entire buffer first.

Keeping lines that match a pattern is useful for large log files then you want to.

Joining and Splitting Lines

Unlike the kill commands that act on lines (C-M-<backspace> and C-k), these commands won’t alter your kill ring. They are also more specialized, as they insert or remove lines with- out moving your point.

Whitespace Commands

Managing whitespace is an issue that recurs often when you yank text from elsewhere or if you work with languages where whitespace is significant.

M-SPC is useful as it trims all whitespace, to the left or right of the point, to a single whitespace character. ving none. M-x cycle-spacing cycles between leaving one, leaving none, and restoring the original spacing.

Transposing text is the act of swapping two syntactic units of text with one another.

C-t: Transpose Characters

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A█BC

After C-t:

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BA█C

Note that the point moved forward one character so you can repeat calls to C-t to “pull” the character to the right:

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BCA█

When you are at the end of a line. C-t will swap the two characters to the left of the point:

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BCA█

After C-t:

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BAC█

This asymmetry is a surprisingly useful way of fixing typos as they occur. Fixing mistyped characters with C-t is a useful time saver as it saves you the effort of deleting both characters and retyping them.

M-t: Transpose Words

Transposing two words with M-t works as you would expect when the words are plain text, like this:

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Hello █World

After M-t:

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World Hello█

Consider this example Python code where we have a dictionary (a key-value hash map):

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names = {
'Jerry':█ 'Seinfeld', 
'Cosmo': 'Kramer',
}

With the point between the key and value, a call to M-t is pure magic:

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names = {
'Seinfeld': 'Jerry', 
'Cosmo': 'Kramer',
}

C-M-t: Transpose S-expressions

Consider what happens if we mix a balanced expression with a word:

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Hello,█ (insert name here)!

After C-M-t:

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(insert name here), Hello█!

Other Transpose Commands

Transposing lines with C-x C-t is useful however. I use it frequently to re-order newline-based lists and it’s also useful for swapping around variable assignments; changing the order functions are called, and so on.

Killing and Yanking Text

Some clipboard-emuivalent commands:

Emacs’s kill commands are best summarized with five simple rules:

• Consecutive kills append to the kill ring. When you kill some words use M-d, and then move to next line and kill another three words. Your last three words are what you yank from the kill ring, not all six! The movement command broken the cycle.

• The kill ring can hold many items and like the undo ring you cannot lose information in the kill ring.

• The kill ring is global and between all the buffers in Emacs. You can view the kill ring - by running C-h v kill-ring.

• Killing is also deleting when you don't care about the killed text.

• Marking is unnecessary for most operations that involve syntactic units. There are two exceptions:

  • If you want to copy(M-w) the region, it's quicker to mark first and then copy.
  • If you want to kill or copy odd-shaped regions that don't conform to multiples of synthetic units.

Appending to the kill ring

Type C-M-w, If next command is a kill command, it will append to the last element in the kill ring.

You can use the method to collect several comments into one big group.

Yanking Text

Cycle through the kill ring is easy:

1. Press C-y where you want the yanked text to appear.
2. Without executing another command - type M-y to step back through Emacs' kill ring.

Basic key bindings

You have several options when Emacs asks you to save a file:

IDO mode

To enable it, type M-x ido-mode and then try C-x b or C-x C-f again.

You can enable it permanently by customizing the option ido-mode:

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M-x customize-option RET ido-mode RET

You can also improve IDO's fuzzy matching by enabling flex matching:

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M-x customize-option RET ido-enable-flex-matching RET

Windows Managment

move between windows with rebinding to M-o , add below to ~/.emacs.d/init.el

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(global-set-key (kbd "M-o") 'other-window)

swich windows with shift key, S-<left>,S-<right>,S-<up>,S-<down>, add below to ~/.emacs.d/init.el

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(windmove-default-keybindings)

Working with other windows

Frame Management

Frames are useful with multi-monitor setups.

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emacs --daemon
emacsclient -nw

Gracefully shutdown daemon

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emacsclient -e '(save-buffers-kill-emacs)'

Getting help

Emacs is a sophisticated self-documenting editor. Every facet of Emacs is searchable or describable.

Emacs’s help system is roughly divided into three parts and knowing which one you need and when will save you time.

The Info Manual

M-x info or C-h i to access.

Look up documentation for a command by typing C-h F and at the prompt enter the name of a command.

Apropos

Describe System

Moving by character

Four fundamental movement

Moving by line

Moving by word

Subword and superword movement

Moving by s-expression

Down and up List

Forward and backward list

Other movement commands

Moving by Paragraph

a set of variables that define the beginning and end of a paragraph:

Moving by sentence

You can alter this behavior by customizing (with M-x customize-option) the following variables:

Moving by Defun

Moving by Pages

Scrolling

In Mac iterm2, you should use M-PageUp and M-PageDn to scroll the other window.

Move to begin and end

When you move to the beginning or end of the buffer, Emacs will place the mark – an invisible location marker – where you came from, so you can return to your old position. For instance, if you type M-< to jump to the beginning of the buffer, you can type C-u C-<SPC> to go back.

Numeric arguments

Move down 50 lines

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M-5 0 C-n

C-u alone has the special meaning of “four times”, moves forward sixteen characters

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C-u C-u C-f

Take a breath and be relax

My favorite player Kobe has gone. So sad these days. The beginning of 2020 seems so hard. Hold on, man, take a breath and be relax. We will win the battle!

We always want run faster, but not solid on the way. We should slow down, make little things right.

Learning basics

• Math basic is so important, calculus, linear algebra, probability. Figure out every detail.
• Emacs, thinking in emacs way, try to forget vim.
• Dig deep into any concept, try to proof each formula.

Sushi and ramen spirit

• Sushi and ramen is a spirit, they tell us to focus on one thing, do it all life time, and do it better.
• To be a coder, we first need have faith, and then working hard, keep going, focus and do one little thing better.

Let's begin

I'll begin the basics from now on. Study every details I face.

8 and 24 R.I.P &

A new day has come!~