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技術社區[雲棲]
我也說說Emacs吧(2) - Emacs其實就是函數的組合
Emacs本質上是函數的組合
從幫助上看emacs有何不同
Vim和Sublime Text等編輯器，本質上是一個編輯器。
比如我們看看vim的幫助，是這個風格的，比如我要看i命令的幫助:
<insert> or *i* *insert* *<Insert>*
i Insert text before the cursor [count] times.
When using CTRL-O in Insert mode |i_CTRL-O| the count
is not supported.
再看看emacs的幫助，是這樣的風格，比如我們看Ctrl-n鍵的幫助:
C-n runs the command next-line (found in global-map), which is an interactive
compiled Lisp function in ‘simple.el’.
It is bound to C-n.
(next-line &optional ARG TRY-VSCROLL)
This function is for interactive use only;
in Lisp code use ‘forward-line’ instead.
Move cursor vertically down ARG lines.
Interactively, vscroll tall lines if ‘auto-window-vscroll’ is enabled.
Non-interactively, use TRY-VSCROLL to control whether to vscroll tall
lines: if either ‘auto-window-vscroll’ or TRY-VSCROLL is nil, this
function will not vscroll.
ARG defaults to 1.
If there is no character in the target line exactly under the current column,
the cursor is positioned after the character in that line which spans this
column, or at the end of the line if it is not long enough.
If there is no line in the buffer after this one, behavior depends on the
value of ‘next-line-add-newlines’. If non-nil, it inserts a newline character
to create a line, and moves the cursor to that line. Otherwise it moves the
cursor to the end of the buffer.
If the variable ‘line-move-visual’ is non-nil, this command moves
by display lines. Otherwise, it moves by buffer lines, without
taking variable-width characters or continued lines into account.
See M-x next-logical-line for a command that always moves by buffer lines.
The command C-x C-n can be used to create
a semipermanent goal column for this command.
Then instead of trying to move exactly vertically (or as close as possible),
this command moves to the specified goal column (or as close as possible).
The goal column is stored in the variable ‘goal-column’, which is nil
when there is no goal column. Note that setting ‘goal-column’
overrides ‘line-move-visual’ and causes this command to move by buffer
lines rather than by display lines.
更進一步，我們可以點擊simple.el進去看看，可以看到它的源碼：
(defun next-line (&optional arg try-vscroll)
"Move cursor vertically down ARG lines.
...就是上麵貼過的幫助，此處略過
"
(declare (interactive-only forward-line))
(interactive "^p\np")
(or arg (setq arg 1))
(if (and next-line-add-newlines (= arg 1))
(if (save-excursion (end-of-line) (eobp))
;; When adding a newline, don't expand an abbrev.
(let ((abbrev-mode nil))
(end-of-line)
(insert (if use-hard-newlines hard-newline "\n")))
(line-move arg nil nil try-vscroll))
(if (called-interactively-p 'interactive)
(condition-case err
(line-move arg nil nil try-vscroll)
((beginning-of-buffer end-of-buffer)
(signal (car err) (cdr err))))
(line-move arg nil nil try-vscroll)))
nil)
從上麵可以看到，比起vim是個相對黑盒，需要文檔描述的編輯器，emacs是個比較簡單直接的家夥。簡單到，基本上就是一堆函數的組合而己，我們做編輯時，就是直接調用這些函數。為了方便，我們把這些函數綁定到快捷鍵上。
隻要知道要調用哪個函數，不想記任何快捷鍵的話，隻需要記住一個就可以了，就是Alt+X，然後就可以輸入要執行的函數名，去執行這個命令。
Emacs的功能，都是由lisp或C語言實現的函數來實現的，所有的源碼都是開放的，在新的版本中，直接都可以通過幫助功能來查看，非常方便。
在emacs裏，Alt鍵的命令也都可以通過先按Esc再按另一個鍵的方式來實現。
從擴展方向上看emacs的不同
vim的擴展
Emacs是第一個著名的以可擴展能力而聞名的編輯器，同時期的主流編輯器在這方麵都要向emacs學習。到了現在，Sublime Text和Vim等編輯器的擴展功能也是非常值得稱道而且受歡迎的。
但是，不管是Vim還是Sublime Text，甚至更強大一些的Visual Studio Code和Atom，它們的做法都是把擴展的接口開放出來，大家按照開放出來的接口來寫擴展。
比如我們先看vim，以我在mac OS下的vim 8.0.600為例，它支持下列feature:
Huge version without GUI. Features included (+) or not (-):
+acl +clipboard +dialog_con +file_in_path +job -lua +mouse_sgr +path_extra +rightleft +tag_old_static +user_commands +writebackup
+arabic +cmdline_compl +diff +find_in_path +jumplist +menu -mouse_sysmouse +perl +ruby -tag_any_white +vertsplit -X11
+autocmd +cmdline_hist +digraphs +float +keymap +mksession +mouse_urxvt +persistent_undo +scrollbind -tcl +virtualedit -xfontset
-balloon_eval +cmdline_info -dnd +folding +lambda +modify_fname +mouse_xterm +postscript +signs +termguicolors +visual -xim
-browse +comments -ebcdic -footer +langmap +mouse +multi_byte +printer +smartindent +terminfo +visualextra -xpm
++builtin_terms +conceal +emacs_tags +fork() +libcall -mouseshape +multi_lang +profile +startuptime +termresponse +viminfo -xsmp
+byte_offset +cryptv +eval -gettext +linebreak +mouse_dec -mzscheme +python +statusline +textobjects +vreplace -xterm_clipboard
+channel +cscope +ex_extra -hangul_input +lispindent -mouse_gpm +netbeans_intg -python3 -sun_workshop +timers +wildignore -xterm_save
+cindent +cursorbind +extra_search +iconv +listcmds -mouse_jsbterm +num64 +quickfix +syntax +title +wildmenu
-clientserver +cursorshape +farsi +insert_expand +localmap +mouse_netterm +packages +reltime +tag_binary -toolbar +windows
帶加號的是我裝的vim支持的功能，減號為不支持。從中可以看到，我用的這個版本的vim支持：python，ruby，perl三種語言，而不支持python3,tcl和lua語言來寫擴展。
比如我們看一個vim擴展的官方例子：
1 " Vim global plugin for correcting typing mistakes
2 " Last Change: 2000 Oct 15
3 " Maintainer: Bram Moolenaar <Bram@vim.org>
4 " License: This file is placed in the public domain.
5
6 if exists("g:loaded_typecorr")
7 finish
8 endif
9 let g:loaded_typecorr = 1
10
11 let s:save_cpo = &cpo
12 set cpo&vim
13
14 iabbrev teh the
15 iabbrev otehr other
16 iabbrev wnat want
17 iabbrev synchronisation
18 \ synchronization
19 let s:count = 4
20
21 if !hasmapto('<Plug>TypecorrAdd')
22 map <unique> <Leader>a <Plug>TypecorrAdd
23 endif
24 noremap <unique> <script> <Plug>TypecorrAdd <SID>Add
25
26 noremenu <script> Plugin.Add\ Correction <SID>Add
27
28 noremap <SID>Add :call <SID>Add(expand("<cword>"), 1)<CR>
29
30 function s:Add(from, correct)
31 let to = input("type the correction for " . a:from . ": ")
32 exe ":iabbrev " . a:from . " " . to
33 if a:correct | exe "normal viws\<C−R>\" \b\e" | endif
34 let s:count = s:count + 1
35 echo s:count . " corrections now"
36 endfunction
37
38 if !exists(":Correct")
39 command −nargs=1 Correct :call s:Add(<q−args>, 0)
40 endif
41
42 let &cpo = s:save_cpo
43 unlet s:save_cpo
在vimscript中，通過exe命令可以執行vim本身的命令。
反正是調用API接口麼，那麼可以支持很多語言了。
比如可以通過:pe perl腳本的方式，直接執行perl語句。可以通過:help :perl查看：
:pe[rl] {cmd} Execute Perl command {cmd}. The current package
is "main".
Perl語言寫vim插件例：
function! WhitePearl()
perl << EOF
VIM::Msg("pearls are nice for necklaces");
VIM::Msg("rubys for rings");
VIM::Msg("pythons for bags");
VIM::Msg("tcls????");
EOF
endfunction
常用的perl可調用接口有：
:perl VIM::Msg("Text") # displays a message
:perl VIM::Msg("Error", "ErrorMsg") # displays an error message
:perl VIM::Msg("remark", "Comment") # displays a highlighted message
:perl VIM::SetOption("ai") # sets a vim option
:perl $nbuf = VIM::Buffers() # returns the number of buffers
:perl @buflist = VIM::Buffers() # returns array of all buffers
:perl $mybuf = (VIM::Buffers('qq.c'))[0] # returns buffer object for 'qq.c'
:perl @winlist = VIM::Windows() # returns array of all windows
:perl $nwin = VIM::Windows() # returns the number of windows
:perl ($success, $v) = VIM::Eval('&path') # $v: option 'path', $success: 1
:perl ($success, $v) = VIM::Eval('&xyz') # $v: '' and $success: 0
:perl $v = VIM::Eval('expand("<cfile>")') # expands <cfile>
:perl $curwin->SetHeight(10) # sets the window height
:perl @pos = $curwin->Cursor() # returns (row, col) array
:perl @pos = (10, 10)
:perl $curwin->Cursor(@pos) # sets cursor to @pos
:perl $curwin->Cursor(10,10) # sets cursor to row 10 col 10
:perl $mybuf = $curwin->Buffer() # returns the buffer object for window
:perl $curbuf->Name() # returns buffer name
:perl $curbuf->Number() # returns buffer number
:perl $curbuf->Count() # returns the number of lines
:perl $l = $curbuf->Get(10) # returns line 10
:perl @l = $curbuf->Get(1 .. 5) # returns lines 1 through 5
:perl $curbuf->Delete(10) # deletes line 10
:perl $curbuf->Delete(10, 20) # delete lines 10 through 20
:perl $curbuf->Append(10, "Line") # appends a line
:perl $curbuf->Append(10, "Line1", "Line2", "Line3") # appends 3 lines
:perl @l = ("L1", "L2", "L3")
:perl $curbuf->Append(10, @l) # appends L1, L2 and L3
:perl $curbuf->Set(10, "Line") # replaces line 10
:perl $curbuf->Set(10, "Line1", "Line2") # replaces lines 10 and 11
:perl $curbuf->Set(10, @l) # replaces 3 lines
類似的，:py可以調用python語言，:rub可以使用ruby語言.
使用python的例子：
:python from vim import *
:python from string import upper
:python current.line = upper(current.line)
:python print "Hello"
:python str = current.buffer[42]
Python調用vim命令的例子：
:py print "Hello" # displays a message
:py vim.command(cmd) # execute an Ex command
:py w = vim.windows[n] # gets window "n"
:py cw = vim.current.window # gets the current window
:py b = vim.buffers[n] # gets buffer "n"
:py cb = vim.current.buffer # gets the current buffer
:py w.height = lines # sets the window height
:py w.cursor = (row, col) # sets the window cursor position
:py pos = w.cursor # gets a tuple (row, col)
:py name = b.name # gets the buffer file name
:py line = b[n] # gets a line from the buffer
:py lines = b[n:m] # gets a list of lines
:py num = len(b) # gets the number of lines
:py b[n] = str # sets a line in the buffer
:py b[n:m] = [str1, str2, str3] # sets a number of lines at once
:py del b[n] # deletes a line
:py del b[n:m] # deletes a number of lines
調用python文件，可以通過:pyfile或:pyf命令調用。
Ruby語言寫vim插件的例子：
function! RedGem()
ruby << EOF
class Garnet
def initialize(s)
@buffer = VIM::Buffer.current
vimputs(s)
end
def vimputs(s)
@buffer.append(@buffer.count,s)
end
end
gem = Garnet.new("pretty")
EOF
endfunction
Ruby調用vim接口的示例：
print "Hello" # displays a message
VIM.command(cmd) # execute an Ex command
num = VIM::Window.count # gets the number of windows
w = VIM::Window[n] # gets window "n"
cw = VIM::Window.current # gets the current window
num = VIM::Buffer.count # gets the number of buffers
b = VIM::Buffer[n] # gets buffer "n"
cb = VIM::Buffer.current # gets the current buffer
w.height = lines # sets the window height
w.cursor = [row, col] # sets the window cursor position
pos = w.cursor # gets an array [row, col]
name = b.name # gets the buffer file name
line = b[n] # gets a line from the buffer
num = b.count # gets the number of lines
b[n] = str # sets a line in the buffer
b.delete(n) # deletes a line
b.append(n, str) # appends a line after n
line = VIM::Buffer.current.line # gets the current line
num = VIM::Buffer.current.line_number # gets the current line number
VIM::Buffer.current.line = "test" # sets the current line number
再來一個lua語言的：
function! CurrentLineInfo()
lua << EOF
local linenr = vim.window().line
local curline = vim.buffer()[linenr]
print(string.format("Current line [%d] has %d chars",
linenr, #curline))
EOF
endfunction
tcl語言的：
function! DefineDate()
tcl << EOF
proc date {} {
return [clock format [clock seconds]]
}
EOF
endfunction
Atom的擴展
Atom的擴展的主力語言是CoffeeScript。
YourNameWordCountView = require './your-name-word-count-view'
{CompositeDisposable} = require 'atom'
module.exports = YourNameWordCount =
yourNameWordCountView: null
modalPanel: null
subscriptions: null
activate: (state) ->
@yourNameWordCountView = new YourNameWordCountView(state.yourNameWordCountViewState)
@modalPanel = atom.workspace.addModalPanel(item: @yourNameWordCountView.getElement(), visible: false)
# Events subscribed to in atom's system can be easily cleaned up with a CompositeDisposable
@subscriptions = new CompositeDisposable
# Register command that toggles this view
@subscriptions.add atom.commands.add 'atom-workspace',
'your-name-word-count:toggle': => @toggle()
deactivate: ->
@modalPanel.destroy()
@subscriptions.dispose()
@wordcountView.destroy()
serialize: ->
yourNameWordCountViewState: @yourNameWordCountView.serialize()
toggle: ->
console.log 'YourNameWordCount was toggled!'
if @modalPanel.isVisible()
@modalPanel.hide()
else
@modalPanel.show()
Visual Studio Code的擴展
Visual Studio Code的插件可以用JavaScript或者TypeScript來開發。
下麵是個空的TypeScript的例子：
// The module 'vscode' contains the VS Code extensibility API
// Import the module and reference it with the alias vscode in your code below
import * as vscode from 'vscode';
// this method is called when your extension is activated
// your extension is activated the very first time the command is executed
export function activate(context: vscode.ExtensionContext) {
// Use the console to output diagnostic information (console.log) and errors (console.error)
// This line of code will only be executed once when your extension is activated
console.log('Congratulations, your extension "my-first-extension" is now active!');
// The command has been defined in the package.json file
// Now provide the implementation of the command with registerCommand
// The commandId parameter must match the command field in package.json
var disposable = vscode.commands.registerCommand('extension.sayHello', () => {
// The code you place here will be executed every time your command is executed
// Display a message box to the user
vscode.window.showInformationMessage('Hello World!');
});
context.subscriptions.push(disposable);
}
Sublime Text的擴展
Sublime Text的擴展是用Python寫的，舉個處理回車換行的例子：
def normalize_line_endings(self, string):
string = string.replace('\r\n', '\n').replace('\r', '\n')
line_endings = self.view.settings().get('default_line_ending')
if line_endings == 'windows':
string = string.replace('\n', '\r\n')
elif line_endings == 'mac':
string = string.replace('\n', '\r')
return string
emacs的擴展
Emacs與以上的編輯器的最大不同的就是，無所謂擴展了，哪塊看不順眼就直接改了就是了。反正大部分都是綁定到快捷鍵上的函數而己。
比如，學習emacs的教程中，最開始講的函數就是find-file，它的作用是打開文件，綁定在C-x C-f鍵上。水木社區官方QQ群進群問題就是問C-x C-f的作用是什麼。
Emacs的好處是沒有秘密，我們直接看源碼，看看它是做啥的：
(defun find-file (filename &optional wildcards)
... ;文檔略
(interactive
(find-file-read-args "Find file: "
(confirm-nonexistent-file-or-buffer)))
(let ((value (find-file-noselect filename nil nil wildcards)))
(if (listp value)
(mapcar 'switch-to-buffer (nreverse value))
(switch-to-buffer value))))
這麼基礎的命令，在其它編輯器中，一般沒人改吧。但是在spacemacs中，C-x C-f就默認綁定ido-find-file函數上了。
(defun ido-find-file ()
(interactive)
(ido-file-internal ido-default-file-method))
ido是Emacs的一個插件，意思是『Interactive Do』，在交互式操作方式上對基礎的Emacs功能上有所增強。
即使在相對古老的emacs 23.x版本上，ido插件也是官方發布版本中的一部分。隻不過官方版本上的鍵綁定還是綁到基礎命令上。我們可以選擇綁一個鍵給它，也可以通過Alt-x來運行它。
後麵學習emacs的功能的時候，我們都會講，標準emacs是如何做的，spacemancs是如何做的。大家可以看到，有很多標準emacs綁定的快捷鍵，在spacemacs上根本就不靈了，被綁定到別的功能上了。
所以，與其記快捷鍵，不如記函數名吧。也不用太精確，輸的時候能找到就行。查幫助時會提升它綁到哪個鍵上，或者記不住就自己綁一個喜歡的也可以。
在Emacs中查找幫助
個人覺得，Emacs的文檔確實不如Vim的文檔寫得好。但是，Emacs的文檔也仍然是非常豐富的，實在查不到，咱還可以直接看代碼。
官網上的文檔
官網上的文檔還是相當豐富的：https://www.gnu.org/software/emacs/manual/
除了基本功能外，常用的大插件的文檔也不少，比如我用emacs寫代碼比較多，經常用cc-mode，cc-mode的文檔也很詳細：https://www.gnu.org/software/emacs/manual/html_node/ccmode/index.html
在emacs中查找幫助
既然我們已經了解到emacs就是一堆函數的組合，那麼提供幫助功能，肯定也是調用相應的函數了。沒錯，正是這樣！
如果想完整地閱讀手冊，可以調用info函數，默認綁定在C-h i組合上。
如果看到手冊或者書上有講一個快捷鍵是做什麼的，我們可以查找它所對應的函數。查找一個按鍵的定義：C-h k (describe-key)：比如我們就可以查查C-h k對應的功能：
C-h k runs the command describe-key, which is an interactive compiled
Lisp function.
It is bound to C-h k, <f1> k, <help> k, <menu-bar> <help-menu>
<describe> <describe-key-1>.
(describe-key &optional KEY UNTRANSLATED UP-EVENT)
Display documentation of the function invoked by KEY.
KEY can be any kind of a key sequence; it can include keyboard events,
mouse events, and/or menu events. When calling from a program,
pass KEY as a string or a vector.
If non-nil, UNTRANSLATED is a vector of the corresponding untranslated events.
It can also be a number, in which case the untranslated events from
the last key sequence entered are used.
UP-EVENT is the up-event that was discarded by reading KEY, or nil.
If KEY is a menu item or a tool-bar button that is disabled, this command
temporarily enables it to allow getting help on disabled items and buttons.
從幫助中我們可以看到，快捷鍵綁到C-h k，而實際調用的函數是describe-key.
同樣，我們還可以通過C-h f (describe-function)來查詢一個函數的功能。
describe-function is an interactive compiled Lisp function.
It is bound to C-h f, <f1> f, <help> f, <menu-bar> <help-menu>
<describe> <describe-function>.
(describe-function FUNCTION)
Display the full documentation of FUNCTION (a symbol).
另外，還有查詢變量的describe-variable函數，綁定到C-h v鍵上。
小結
- emacs的基本用法，就是調用一些函數而己。這些函數可以通過Alt-x加上函數名去調用。
- 常用函數可以綁定到一些快捷鍵上。很多emacs入門教程講的就是這些功能的用法
- info用於在emacs中查看手冊, describe-funciton查找函數用法,對於lisp函數經常可以直達源碼。describe-key查找鍵值綁定。它們默認的綁定是C-h i, C-h f和C-h k。在以後的emacs歲月裏，您會經常用到它們的
最後更新：2017-05-27 17:31:23