01.semantic-keybinding-en.org

01.Semantic-Keybinding

From the prelude, Emacs big-bang its universe simply from M-x. It invoke interactive functions with M(Meta)-x(Execute).

Then it go one more step, replaces the double keys of M-x with the single key of Ctrl, and even further truncates function’s name to its initial letter.

Now instead of redundant M-x forward-char, we straightforwardly strike C-f to move cursor forward a character.

The logic here is obvious: C (Ctrl) substitutes for M (Meta)-x, while f for forward-char.

We pause a moment here to organize our thoughts.

1. Key “Meta” has source meaning in etymology, so it is applied to invoke full-name functions,
2. Key “Ctrl” corresponds to “Command”
3. Key “f” is abbreviated for “forward-character”

So differs from Vim, we could easily conclude that Emacs was designed to bind keys semantically.

With such semantic key bindings, we could manipulate Emacs smoothly as veterans even without remembering one key binding.

The subsequent sessions starts to the cursor movement semantically from:

1. Character and Word
2. Line and Sentence
3. Vertical movement
4. Vertically Page down and up
5. Buffer
6. Logic Text Unit
7. Keys layout
8. Concepts

1.Character and Word

C-f (M-x forward-char) Move cursor forward a character C-b (M-x backward-char) Move cursor backward a character

Character is the minimal unit to operate, and beyond character is word. Now we recall the etymology of “Meta” which means “higher and beyond”.

So “Meta” domains more scope than “Ctrl”, if they bind identical keys, then we have:

M-f (M-x forward-word) Move cursor forward a word (higher than character) M-b (M-x backward -word) Move cursor backward a word

2.Line and Sentence

C-e (e for end) Move cursor to end end of line C-a (a for ahead) Move cursor to ahead of line

Again with same logic, “Meta” is in charge more than “Ctrl”. A sentence might extend to multiple lines so it is larger than line.

M-e Move cursor to end of sentence M-a Move cursor to ahead of sentence

The above sections are all about move cursor horizontally. Corresponding to them are vertical movements.

3.Vertical Movement

C-n (M-x next-line) Move cursor to next line C-p (M-x previous-line) Move cursor to previous line

How about “M-n” and “M-p” which are expected to govern more territory.

The truth is that vanilla Emacs does not define them, and leave us a golden opportunity.

We’ll come back for the opportunity later.

4.Vertically Page Down and Up

M-v Scroll one page up C-v Scroll one page down

It’s apparent that a “V” in “M-v” means “vertical”. We also be aware that Meta is higher.So Meta-Vertical is to move vertically higher up.

In contrast to Meta as higher, we choose Ctrl which domains less area as lower. So Ctrl-Vertical is to move cursor vertically lower down.

When having a second thinking on such bindings, we might find it more semantically clear if bind triple keys as “M-v-u(up)” and “M-v-d(down)” than the above double key bindings.

The idea behind is that triple keys-sequence are redundant and time-consuming. We utilize less keys to get more jobs done.

“M-v” and “C-v” help us scroll by the whole page. However, what we want usually is to scroll half page or multiple lines.

Now we restore to “M-p” and “M-n” in 3.Vertical Movement which should control more than single line as “C-p” and “C-n”:

Therefore, we define functions of “previous-multilines” and “next-multilines” and bind them to “M-p” and “M-n”.

(defun previous-multilines ()
  "scroll down multiple lines"
  (interactive)
  (scroll-down (/ (window-body-height) 3)))

(defun next-multilines ()
  "scroll up multiple lines"
  (interactive)
  (scroll-up (/ (window-body-height) 3)))

(global-set-key "\M-n" 'next-multilines) ;;custom
(global-set-key "\M-p" 'previous-multilines) ;;custom

I configure “Invert scroll direction(Natural Scrolling)” in touch-pad and mouse , so “up and down” are reversely map to “next and previous”.

5.Buffer

M-< (Move cursor to the beginning of the buffer) M-> (Move cursor to the end of the buffer)

Please notice that the power of “Ctrl” just stretch up to “line”, and all the left higher segments(sentence, paragraph etc) are dominated by “Meta”.

6.Text Unit

• Paragraph

  M-{

  Move back to previous paragraph beginning (backward-paragraph).

  M-}

  Move forward to next paragraph end (forward-paragraph).

  M-h

  Put point and mark around this or next paragraph (mark-paragraph).

• Pages

  M-x

  what-page Display the page number of point, and the line number within that page.

  C-x [

  Move point to previous page boundary (backward-page).

  C-x ]

  Move point to next page boundary (forward-page).

  C-x C-p

  Put point and mark around this page (or another page) (mark-page).

  C-x l

  Count the lines in this page (count-lines-page).

7.Keys Layout

Suppose to lay keys as:

Alt(option) --> Ctrl --> Space <-- Ctrl <--Alt

Keep the layout on whatever keyboard.

8.Fundamental Concepts

In Emacs, we call cursor a special name as “point”, and the selected area as “region”. “Point” is starting end of the region while “Mark” is the end point.

Command	Description
C-@	Set mark
C-Spc	same as C-@
C-x C-x	Interchange mark and point
M-@	set mark after next word
M-h	region around paragraph
C-x h	Put region around entire buffer

9.Summary

Emacs starts everything from M-x, then employ “Ctrl” to facilitate it and expand it universe with semantic key-bindings.