Viper Is a Package for Emacs Rebels: 2. Improvements over Vi

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# 2. Improvements over Vi

Some common problems with Vi and Ex have been solved in Viper. This includes better implementation of existing commands, new commands, and the facilities provided by Emacs.

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## 2.1 Basics

The Vi command set is based on the idea of combining motion commands with other commands. The motion command is used as a text region specifier for other commands. We classify motion commands into point commands and line commands.

The point commands are:

> `h`, `l`, `0`, `$`, `w`, `W`, `b`, `B`, `e`, `E`, `(`, `)`, `/`, `?`, ```, `f`, `F`, `t`, `T`, `%`, `;`, `,`, `^`

The line commands are:

> `j`, `k`, `+`, `-`, `H`, `M`, `L`, `{`, `}`, `G`, `'`, `[[`, `]]`, `[]`

If a point command is given as an argument to a modifying command, the region determined by the point command will be affected by the modifying command. On the other hand, if a line command is given as an argument to a modifying command, the region determined by the line command will be enlarged so that it will become the smallest region properly containing the region and consisting of whole lines (we call this process expanding the region), and then the enlarged region will be affected by the modifying command. Text Deletion Commands (see section Deleting Text), Change commands (see section Changing Text), even Shell Commands (see section Shell Commands) use these commands to describe a region of text to operate on. Thus, type `dw` to delete a word, `>}` to shift a paragraph, or `!'afmt` to format a region from ‘`point`’ to textmarker ‘`a`’.

Viper adds the region specifiers ‘`r`’ and ‘`R`’. Emacs has a special marker called mark. The text-area between the current cursor position point and the mark is called the region. ‘`r`’ specifies the raw region and ‘`R`’ is the expanded region (i.e., the minimal contiguous chunk of full lines that contains the raw region). `dr` will now delete the region, `>r` will shift it, etc. `r,R` are not motion commands, however. The special mark is set by `m.` and other commands. See section Marking, for more info.

Viper also adds counts to most commands for which it would make sense.

In the Overview chapter, some Multiple File issues were discussed (see section Multiple Files in Viper). In addition to the files, Emacs has buffers. These can be seen in the `:args` list and switched using `:next` if you type `:set ex-cycle-through-non-files t`, or specify `(setq ex-cycle-through-non-files t)` in your ‘`.viper`’ file. See section Customization, for details.

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## 2.2 Undo and Backups

Viper provides multiple undo. The number of undo’s and the size is limited by the machine. The Viper command `u` does an undo. Undo can be repeated by typing `.` (a period). Another `u` will undo the undo, and further `.` will repeat it. Typing `u` does the first undo, and changes the direction.

Since the undo size is limited, Viper can create backup files and auto-save files. It will normally do this automatically. It is possible to have numbered backups, etc. For details, see (emacs)Backup section ‘Backup and Auto-Save’ in The GNU Emacs Manual

The results of the 9 previous changes are available in the 9 numeric registers, as in Vi. The extra goody is the ability to view these registers, in addition to being able to access them through `p` and `M-y` (See section Insert State, for details.) The Viper command `] register` will display the contents of any register, numeric or alphabetical. The related command `[ textmarker` will show the text around the textmarker. ‘`register`’ and ‘`textmarker`’ can be any letters from a through z.

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## 2.3 History

History is provided for Ex commands, Vi searches, file names, pieces of text inserted in earlier commands that use Insert or Replace state, and for destructive commands in Vi state. These are useful for fixing those small typos that screw up searches and `:s`, and for eliminating routine associated with repeated typing of file names or pieces of text that need to be inserted frequently. At the `:` or `/` prompts in the Minibuffer, you can do the following:

`M-p and M-n`

  To move to previous and next history items. This causes the history items to appear on the command line, where you can edit them, or simply type Return to execute.

`M-r and M-s`

  To search backward and forward through the history.

`<RET>`

  Type <RET> to accept a default (which is displayed in the prompt).

The history of insertions can be perused by typing `C-c M-p` and `C-c M-n` while in Insert or Replace state. The history of destructive Vi commands can be perused via the same keys when Viper is in Vi state. See section Viper Specials, for details.

All Ex commands have a file history. For instance, typing `:e`, space and then `M-p` will bring up the name of the previously typed file name. Repeatedly typing `M-p`, `M-n`, etc., will let you browse through the file history.

Similarly, commands that have to do with switching buffers have a buffer history, and commands that expect strings or regular expressions keep a history on those items.

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## 2.4 Macros and Registers

Viper facilitates the use of Emacs-style keyboard macros. `@#` will start a macro definition. As you type, the commands will be executed, and remembered (This is called “learn mode” in some editors.) `@register` will complete the macro, putting it into ‘`register`’, where ‘`register`’ is any character from ‘`a`’ through ‘`z`’. Then you can execute this macro using `@register`. It is, of course, possible to yank some text into a register and execute it using `@register`. Typing `@@`, `@RET`, or `@C-j` will execute the last macro that was executed using `@register`.

Viper will automatically lowercase the register, so that pressing the `SHIFT` key for `@` will not create problems. This is for `@` macros and `"p` only. In the case of `y`, `"Ayy` will append to register a. For `[,],',``, it is an error to use a Uppercase register name.

The contents of a register can be seen by `]register`. (`[textmarker` will show the contents of a textmarker).

The last keyboard macro can also be executed using `*`, and it can be yanked into a register using `@!register`. This is useful for Emacs style keyboard macros defined using `C-x(` and `C-x)`. Emacs keyboard macros have more capabilities. See (emacs)Keyboard Macros section ‘Keyboard Macros’ in The GNU Emacs Manual, for details.

Keyboard Macros allow an interesting form of Query-Replace: `/pattern` or `n` to go to the next pattern (the query), followed by a Keyboard Macro execution `@@` (the replace).

Viper also provides Vi-style macros. See section Vi Macros, for details.

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## 2.5 Completion

Completion is done when you type <TAB>. The Emacs completer does not grok wildcards in file names. Once you type a wildcard, the completer will no longer work for that file name. Remember that Emacs interprets a file name of the form `/foo//bar` as `/bar` and `/foo/~/bar` as `~/bar`.

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## 2.6 Improved Search

Viper provides buffer search, the ability to search the buffer for a region under the cursor. You have to turn this on in ‘`.viper`’ either by calling

    (viper-buffer-search-enable)

or by setting `viper-buffer-search-char` to, say, `f3`:

    (setq viper-buffer-search-char ?g)

If the user calls `viper-buffer-search-enable` explicitly (the first method), then `viper-buffer-search-char` will be set to `g`. Regardless of how this feature is enabled, the key `viper-buffer-search-char` will take movement commands, like `w,/,e`, to find a region and then search for the contents of that region. This command is very useful for searching for variable names, etc., in a program. The search can be repeated by `n` or reversed by `N`.

Emacs provides incremental search. As you type the string in, the cursor will move to the next match. You can snarf words from the buffer as you go along. Incremental Search is normally bound to `C-s` and `C-r`. See section Customization, to find out how to change the bindings of `C-r or C-s`. For details, see (emacs)Incremental Search section ‘Incremental Search’ in The GNU Emacs Manual

Viper also provides a query replace function that prompts through the Minibuffer. It is invoked by the `Q` key in Vi state.

On a window display, Viper supports mouse search, i.e., you can search for a word by clicking on it. See section Viper Specials, for details.

Finally, on a window display, Viper highlights search patterns as it finds them. This is done through what is known as faces in Emacs. The variable that controls how search patterns are highlighted is `viper-search-face`. If you don’t want any highlighting at all, put

    (copy-face 'default 'viper-search-face)

in ‘`~/.viper`’. If you want to change how patterns are highlighted, you will have to change `viper-search-face` to your liking. The easiest way to do this is to use Emacs customization widget, which is accessible from the menubar. Viper customization group is located under the Emulations customization group, which in turn is under the Editing group (or simply by typing `:customize`). All Viper faces are grouped together under Viper’s Highlighting group.

Try it: it is really simple!

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## 2.7 Abbreviation Facilities

It is possible in Emacs to define abbrevs based on the contents of the buffer. Sophisticated templates can be defined using the Emacs abbreviation facilities. See (emacs)Abbrevs section ‘Abbreviations’ in The GNU Emacs Manual, for details.

Emacs also provides Dynamic Abbreviations. Given a partial word, Emacs will search the buffer to find an extension for this word. For instance, one can type ‘`Abbreviations`’ by typing ‘`A`’, followed by a keystroke that completed the ‘`A`’ to ‘`Abbreviations`’. Repeated typing will search further back in the buffer, so that one could get ‘`Abbrevs`’ by repeating the keystroke, which appears earlier in the text. Emacs binds this to `<ESC> /`, so you will have to find a key and bind the function `dabbrev-expand` to that key. Facilities like this make Vi’s `:ab` command obsolete.

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## 2.8 Movement and Markers

Viper can be set free from the line–limited movements in Vi, such as `l` refusing to move beyond the line, <ESC> moving one character back, etc. These derive from Ex, which is a line editor. If your ‘`.viper`’ contains

    (setq viper-ex-style-motion nil)

the motion will be a true screen editor motion. One thing you must then watch out for is that it is possible to be on the end-of-line character. The keys `x` and `%` will still work correctly, i.e., as if they were on the last character.

The word-movement commands `w`, `e`, etc., and the associated deletion/yanking commands, `dw`, `yw`, etc., can be made to understand Emacs syntax tables. If the variable `viper-syntax-preference` is set to `strict-vi` then the meaning of word is the same as in Vi. However, if the value is `reformed-vi` (the default) then the alphanumeric symbols will be those specified by the current Emacs syntax table (which may be different for different major modes) plus the underscore symbol `_`, minus some non-word symbols, like ’.;,|, etc. Both `strict-vi` and `reformed-vi` work close to Vi in traditional cases, but `reformed-vi` does a better job when editing text in non-Latin alphabets.

The user can also specify the value `emacs`, which would make Viper use exactly the Emacs notion of word. In particular, the underscore may not be part of a word. Finally, if `viper-syntax-preference` is set to `extended`, Viper words would consist of characters that are classified as alphanumeric or as parts of symbols. This is convenient for writing programs and in many other situations.

`viper-syntax-preference` is a local variable, so it can have different values for different major modes. For instance, in programming modes it can have the value `extended`. In text modes where words contain special characters, such as European (non-English) letters, Cyrillic letters, etc., the value can be `reformed-vi` or `emacs`.

Changes to `viper-syntax-preference` should be done in the hooks to various major modes by executing `viper-set-syntax-preference` as in the following example:

    (viper-set-syntax-preference nil "emacs")

The above discussion of the meaning of Viper’s words concerns only Viper’s movement commands. In regular expressions, words remain the same as in Emacs. That is, the expressions `\w`, `\>`, `\<`, etc., use Emacs’ idea of what is a word, and they don’t look into the value of variable `viper-syntax-preference`. This is because Viper doesn’t change syntax tables in fear of upsetting the various major modes that set these tables.

Textmarkers in Viper remember the file and the position, so that you can switch files by simply doing `'a`. If you set up a regimen for using Textmarkers, this is very useful. Contents of textmarkers can be viewed by `[marker`. (Contents of registers can be viewed by `]register`).

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## 2.9 New Commands

These commands have no Vi analogs.

`C-x, C-c`

  These two keys invoke many important Emacs functions. For example, if you hit `C-x` followed by `2`, then the current window will be split into 2. Except for novice users, `C-c` is also set to execute an Emacs command from the current major mode. <ESC> will do the same, if you configure <ESC> as Meta by setting `viper-no-multiple-ESC` to nil in ‘`.viper`’. See section Customization. `C-\` in Insert, Replace, or Vi states will make Emacs think `Meta` has been hit.

`\`

  Escape to Emacs to execute a single Emacs command. For instance, `\ <ESC>` will act like a Meta key.

`Q`

  `Q` is for query replace. By default, each string to be replaced is treated as a regular expression. You can use `(setq viper-re-query-replace nil)` in your ‘`.emacs`’ file to turn this off. (For normal searches, `:se nomagic` will work. Note that `:se nomagic` turns Regexps off completely, unlike Vi).

`v`
`V`
`C-v`

  These keys are used to visit files. `v` will switch to a buffer visiting file whose name can be entered in the Minibuffer. `V` is similar, but will use a window different from the current window. `C-v` is like `V`, except that a new frame (X window) will be used instead of a new Emacs window.

`#`

  If followed by a certain character ch, it becomes an operator whose argument is the region determined by the motion command that follows (indicated as <move>). Currently, ch can be one of `c`, `C`, `g`, `q`, and `s`. For instance, `#qr` will prompt you for a string and then prepend this string to each line in the buffer.

`# c`

  Change upper-case characters in the region to lower-case (`downcase-region`). Emacs command `M-l` does the same for words.

`# C`

  Change lower-case characters in the region to upper-case. For instance, `# C 3 w` will capitalize 3 words from the current point (`upcase-region`). Emacs command `M-u` does the same for words.

`# g`

  Execute last keyboard macro for each line in the region (`viper-global-execute`).

`# q`

  Insert specified string at the beginning of each line in the region (`viper-quote-region`). The default string is composed of the comment character(s) appropriate for the current major mode.

`# s`

  Check spelling of words in the region (`spell-region`). The function used for spelling is determined from the variable `viper-spell-function`.

`*`

  Call last keyboard macro.

`m .`

  Set mark at point and push old mark off the ring

`m<`
`m>`

  Set mark at beginning and end of buffer, respectively.

`m,`

  Jump to mark and pop mark off the ring. See (emacs)Mark section ‘Mark’ in The GNU Emacs Manual, for more info.

`] register`

  View contents of register

`[ textmarker`

  View filename and position of textmarker

`@#`
`@register`
`@!`

  Begin/end keyboard macro. @register has a different meaning when used after a `@#`. See section Macros and Registers, for details

`[]`

  Go to end of heading.

`g <movement command>`

  Search buffer for text delimited by movement command. The canonical example is `gw` to search for the word under the cursor. See section Improved Search, for details.

`C-g and C-]`

  Quit and Abort Recursive edit. These may be necessary on occasion. See section Vi State, for a reason.

`C-c C-g`

  Hitting `C-c` followed by `C-g` will display the information on the current buffer. This is the same as hitting `C-g` in Vi, but, as explained above, `C-g` is needed for other purposes in Emacs.

`C-c /`

  Without a prefix argument, this command toggles case-sensitive/case-insensitive search modes and plain vanilla/regular expression search. With the prefix argument 1, i.e., `1 C-c /`, this toggles case-sensitivity; with the prefix argument 2, toggles plain vanilla search and search using regular expressions. See section Viper Specials, for alternative ways to invoke this function.

`M-p and M-n`

  In the Minibuffer, these commands navigate through the minibuffer histories, such as the history of search strings, Ex commands, etc.

`C-c M-p and C-c M-n`

  In Insert or Replace state, these commands let the user peruse the history of insertion strings used in previous insert or replace commands. Try to hit `C-c M-p` or `C-c M-n` repeatedly and see what happens. See section Viper Specials, for more.

  In Vi state, these commands let the user peruse the history of Vi-style destructive commands, such as `dw`, `J`, `a`, etc. By repeatedly typing `C-c M-p` or `C-c M-n` you will cycle Viper through the recent history of Vi commands, displaying the commands one by one. Once an appropriate command is found, it can be executed by typing ‘`.`’.

  Since typing `C-c M-p` is tedious, it is more convenient to bind an appropriate function to a function key on the keyboard and use that key. See section Viper Specials, for details.

`Ex commands`

  The commands `:args`, `:next`, `:pre` behave differently. `:pwd` exists to get current directory. The commands `:b` and `:B` switch buffers around. See section File and Buffer Handling, for details. There are also the new commands `:RelatedFile` and `PreviousRelatedFile` (which abbreviate to `R` and `P`, respectively. See section Viper Specials, for details.

Apart from the new commands, many old commands have been enhanced. Most notably, Vi style macros are much more powerful in Viper than in Vi. See section Vi Macros, for details.

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## 2.10 Useful Packages

Some Emacs packages are mentioned here as an aid to the new Viper user, to indicate what Viper is capable of. A vast number comes with the standard Emacs distribution, and many more exist on the net and on the archives.

This manual also mentions some Emacs features a new user should know about. The details of these are found in the GNU Emacs Manual.

The features first. For details, look up the Emacs Manual.

‘`Make`’

  Makes and Compiles can be done from the editor. Error messages will be parsed and you can move to the error lines.

‘`Shell`’

  You can talk to Shells from inside the editor. Your entire shell session can be treated as a file.

‘`Mail`’

  Mail can be read from and sent within the editor. Several sophisticated packages exist.

‘`Language Sensitive Editing`’

  Editing modes are written for most computer languages in existence. By controlling indentation, they catch punctuation errors.

The packages, below, represents a drop in the sea of special-purpose packages that come with standard distribution of Emacs.

‘`Transparent FTP`’

  `ange-ftp.el` can ftp from the editor to files on other machines transparent to the user.

‘`RCS Interfaces`’

  `vc.el` for doing RCS commands from inside the editor

‘`Directory Editor`’

  `dired.el` for editing contents of directories and for navigating in the file system.

‘`Syntactic Highlighting`’

  `font-lock.el` for automatic highlighting various parts of a buffer using different fonts and colors.

‘`Saving Emacs Configuration`’

  `desktop.el` for saving/restoring configuration on Emacs exit/startup.

‘`Spell Checker`’

  `ispell.el` for spell checking the buffer, words, regions, etc.

‘`File and Buffer Comparison`’

  `ediff.el` for finding differences between files and for applying patches.

Emacs Lisp archives exist on ‘`archive.cis.ohio-state.edu`’ and ‘`wuarchive.wustl.edu`’

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