viper: Groundwork
4.1 Groundwork
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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’, ‘$’, ‘w’, ‘W’, ‘b’, ‘B’, ‘e’, ‘E’, ‘(’, ‘)’, ‘/’,
‘?’, ‘`’, ‘f’, ‘F’, ‘t’, ‘T’, ‘%’, ‘;’, ‘,’, ‘^’
The line commands are:
‘j’, ‘k’, ‘+’, ‘-’, ‘H’, ‘M’, ‘L’, ‘{’, ‘}’, ‘G’, ‘'’, ‘[[’, ‘]]’,
‘[]’
Text Deletion Commands (
Deleting Text), Change commands
(Changing Text), even Shell Commands (Shell Commands)
use these commands to describe a region of text to operate on.
Viper adds two region descriptors, ‘r’ and ‘R’. These describe the
Emacs regions (Basics), but they are not movement commands.
The command description uses angle brackets ‘<>’ to indicate
metasyntactic variables, since the normal conventions of using simple
text can be confusing with Viper where the commands themselves are
characters. Watch out where ‘<’ shift commands and ‘<count>’ are
mentioned together!!!
‘<move>’ refers to the above movement commands, and ‘<a-z>’ refers to
registers or textmarkers from ‘a’ to ‘z’. Note that the ‘<move>’ is
described by full move commands, that is to say they will take counts,
and otherwise behave like normal move commands. ‘<address>’ refers to
Ex line addresses, which include
‘. <No address>’
Current line
‘.+n .-n’
Add or subtract for current line
‘number’
Actual line number, use ‘.=’ to get the line number
‘'<a-z>’
Textmarker
‘$’
Last line
‘x,y’
Where x and y are one of the above
‘%’
For the whole file, same as (1,$).
‘/<pat>/’
‘?<pat>?’
Next or previous line with pattern <pat>.
Note that the pattern is allowed to contain newline character
(inserted as ‘C-qC-j’). Therefore, one can search for patterns
that span several lines.
Note that ‘%’ is used in Ex commands ‘:e’ and ‘:r <shell-cmd>’ to
mean current file. If you want a ‘%’ in your command, it must be
escaped as ‘\%’. Note that ‘:w’ and the regular ‘:r <file>’ command
doesn’t support the meta symbols ‘%’ and ‘#’, because file history is a
better mechanism. Similarly, ‘#’ expands to the previous file. The
previous file is the first file in ‘:args’ listing. This defaults to
previous window in the VI sense if you have one window only.
Others like ‘<args> -- arguments’, ‘<cmd> -- command’ etc. should be
fairly obvious.
Common characters referred to include:
‘<sp>’
Space
‘<ht>’
Tab
‘<lf>’
Linefeed
‘<esc>’
Escape
‘<cr>’
Return, Enter
We also use ‘word’ for alphanumeric/non-alphanumeric words, and
‘WORD’ for whitespace delimited words. ‘char’ refers to any ASCII
character, ‘CHAR’ to non-whitespace character. Brackets ‘[]’ indicate
optional parameters; ‘<count>’ also optional, usually defaulting to 1.
Brackets are elided for ‘<count>’ to eschew obfuscation.
Viper’s idea of Vi’s words is slightly different from Vi. First,
Viper words understand Emacs symbol tables. Therefore, all symbols
declared to be alphanumeric in a symbol table can automatically be made
part of the Viper word. This is useful when, for instance, editing text
containing European, Cyrillic, Japanese, etc., texts.
Second, Viper lets you depart from Vi’s idea of a word by changing
the a syntax preference via the customization widget (the variable
‘viper-syntax-preference’) or by executing ‘viper-set-syntax-preference’
interactively.
By default, Viper syntax preference is ‘reformed-vi’, which means
that Viper considers only those symbols to be part of a word that are
specified as word-symbols by the current Emacs syntax table (which may
be different for different major modes) plus the underscore symbol ‘_’,
minus the symbols that are not considered words in Vi (e.g., ‘,’, ‘;’,
etc.), but may be considered as word-symbols by various Emacs major
modes. Reformed-Vi works very close to Vi, and it also recognizes words
in other alphabets. Therefore, this is the most appropriate mode for
editing text and is likely to fit all your needs.
You can also set Viper syntax preference to ‘strict-vi’, which would
cause Viper to view all non-English letters as non-word-symbols.
You can also specify ‘emacs’ as your preference, which would make
Viper use exactly the same notion of a word as Emacs does. In
particular, the underscore may not be part of a word in some major
modes.
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 editing programs.
‘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’. If you consider using different syntactic preferences for
different major modes, you should execute, for example,
(viper-set-syntax-preference nil "extended")
in the appropriate major mode hooks.
The above discussion concerns only the movement commands. In regular
expressions, words remain the same as in Emacs. That is, the
expressions ‘\w’, ‘\>’, ‘\<’, etc., use Emacs’s idea of what is a word,
and they don’t look into the value of variable
‘viper-syntax-preference’. This is because Viper avoids changing syntax
tables in order to not thwart the various major modes that set these
tables.
The usual Emacs convention is used to indicate Control Characters,
i.e., C-h for Control-h. _Do not confuse this with a sequence of
separate characters C, -, h!!!_ The ‘^’ is itself, never used to
indicate a Control character.
Finally, we note that Viper’s Ex-style commands can be made to work
on the current Emacs region. This is done by typing a digit argument
before ‘:’. For instance, typing ‘1:’ will prompt you with something
like _:123,135_, assuming that the current region starts at line 123 and
ends at line 135. There is no need to type the line numbers, since
Viper inserts them automatically in front of the Ex command.
Info Catalog
viper: Commands
viper: Text Handling