# Vim documentation: if_lua

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    *if_lua.txt*    For Vim version 7.3f.  Last change: 2010 Jul 22

    		  VIM REFERENCE MANUAL    by Luis Carvalho

    The Lua Interface to Vim				*lua* *Lua*

    1. Commands			|lua-commands|
    2. The vim module		|lua-vim|
    3. Buffer userdata		|lua-buffer|
    4. Window userdata		|lua-window|

    {Vi does not have any of these commands}

    The Lua interface is available only when Vim was compiled with the
    |+lua| feature.

    ==============================================================================

    1. Commands						*lua-commands*

    							*:lua*
    :[range]lua {chunk}
    			Execute Lua chunk {chunk}.    {not in Vi}

    Examples:

    	:lua print("Hello, Vim!")
    	:lua local curbuf = vim.buffer() curbuf[7] = "line #7"

    :[range]lua << {endmarker}
    {script}
    {endmarker}
    			Execute Lua script {script}.  {not in Vi}
    			Note: This command doesn't work when the Lua
    			feature wasn't compiled in.  To avoid errors, see
    			|script-here|.

    {endmarker} must NOT be preceded by any white space.  If {endmarker} is
    omitted from after the "<<", a dot '.' must be used after {script}, like
    for the |:append| and |:insert| commands.
    This form of the |:lua| command is mainly useful for including Lua code
    in Vim scripts.

    Example:

    	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

    							*:luado*
    :[range]luado {body}	Execute Lua function "function (line) {body} end" for
    			each line in the [range], with the function argument
    			being set to the text of each line in turn, without a
    			trailing <EOL>. If the value returned by the function
    			is a string it becomes the text of the line in the
    			current turn. The default for [range] is the whole
    			file: "1,$".		      {not in Vi}

    Examples:

    	:luado return string.format("%s\t%d", line:reverse(), #line)

    	:lua require"lpeg"
    	:lua -- balanced parenthesis grammar:
    	:lua bp = lpeg.P{ "(" * ((1 - lpeg.S"()") + lpeg.V(1))^0 * ")" }
    	:luado if bp:match(line) then return "-->\t" .. line end

    							*:luafile*
    :[range]luafile {file}
    			Execute Lua script in {file}. {not in Vi}
    			The whole argument is used as a single file name.

    Examples:

    	:luafile script.lua
    	:luafile %

    All these commands execute a Lua chunk from either the command line (:lua and
    :luado) or a file (:luafile) with the given line [range]. Similarly to the Lua
    interpreter, each chunk has its own scope and so only global variables are
    shared between command calls. Lua default libraries "table", "string", "math",
    and "package" are available, "io" and "debug" are not, and "os" is restricted
    to functions "date", "clock", "time", "difftime", and "getenv". In addition,
    Lua "print" function has its output redirected to the Vim message area, with
    arguments separated by a white space instead of a tab.

    Lua uses the "vim" module (see |lua-vim|) to issue commands to Vim
    and manage buffers (|lua-buffer|) and windows (|lua-window|). However,
    procedures that alter buffer content, open new buffers, and change cursor
    position are restricted when the command is executed in the |sandbox|.

    ==============================================================================

    2. The vim module					*lua-vim*

    Lua interfaces Vim through the "vim" module. The first and last line of the
    input range are stored in "vim.firstline" and "vim.lastline" respectively. The
    module also includes routines for buffer, window, and current line queries,
    Vim evaluation and command execution, and others.

    	vim.isbuffer(value)	Returns 'true' (boolean, not string) if
    				"value" is a buffer userdata and 'false'
    				otherwise (see |lua-buffer|).

    	vim.buffer([arg])	If "arg" is a number, returns buffer with
    				number "arg" in the buffer list or, if "arg"
    				is a string, returns buffer whose full or short
    				name is "arg". In both cases, returns 'nil'
    				(nil value, not string) if the buffer is not
    				found. Otherwise, if "toboolean(arg)" is
    				'true' returns the first buffer in the buffer
    				list or else the current buffer.

    	vim.iswindow(value)	Returns 'true' (boolean, not string) if
    				"value" is a window userdata and
    				'false' otherwise (see |lua-window|).

    	vim.window([arg])	If "arg" is a number, returns window with
    				number "arg" or 'nil' (nil value, not string)
    				if not found. Otherwise, if "toboolean(arg)"
    				is 'true' returns the first window or else the
    				current window.

    	vim.command({cmd})	Executes the vim (ex-mode) command {cmd}.
    				Examples:
    					:lua vim.command"set tw=60"
    					:lua vim.command"normal ddp"

    	vim.eval({expr})	Evaluates expression {expr} (see |expression|),
    				converts the result to Lua, and returns it.
    				Vim strings and numbers are directly converted
    				to Lua strings and numbers respectively. Vim
    				lists and dictionaries are converted to Lua
    				tables (lists become integer-keyed tables).
    				Examples:
    					:lua tw = vim.eval"&tw"
    					:lua print(vim.eval"{'a': 'one'}".a)

    	vim.line()		Returns the current line (without the trailing
    				<EOL>), a Lua string.

    	vim.beep()		Beeps.

    	vim.open({fname})	Opens a new buffer for file {fname} and
    				returns it. Note that the buffer is not set as
    				current.

    ==============================================================================

    3. Buffer userdata					*lua-buffer*

    Buffer userdata represent vim buffers. A buffer userdata "b" has the following
    properties and methods:

    Properties
    	o "b()" sets "b" as the current buffer.
    	o "#b" is the number of lines in buffer "b".
    	o "b[k]" represents line number k: "b[k] = newline" replaces line k
    	    with string "newline" and "b[k] = nil" deletes line k.
    	o "b.name" contains the short name of buffer "b" (read-only).
    	o "b.fname" contains the full name of buffer "b" (read-only).
    	o "b.number" contains the position of buffer "b" in the buffer list
    	    (read-only).

    Methods
    	o "b:insert(newline[, pos])" inserts string "newline" at (optional)
    	    position "pos" in the buffer. The default value for "pos" is
    	    "#b + 1". If "pos == 0" then "newline" becomes the first line in
    	    the buffer.
    	o "b:next()" returns the buffer next to "b" in the buffer list.
    	o "b:previous()" returns the buffer previous to "b" in the buffer
    	    list.
    	o "b:isvalid()" returns 'true' (boolean) if buffer "b" corresponds to
    	    a "real" (not freed from memory) Vim buffer.

    Examples:

    	:lua b = vim.buffer() -- current buffer
    	:lua print(b.name, b.number)
    	:lua b[1] = "first line"
    	:lua b:insert("FIRST!", 0)
    	:lua b[1] = nil -- delete top line
    	:lua for i=1,3 do b:insert(math.random()) end
    	:3,4lua for i=vim.lastline,vim.firstline,-1 do b[i] = nil end
    	:lua vim.open"myfile"() -- open buffer and set it as current

    	function! ListBuffers()
    	lua << EOF
    	local b = vim.buffer(true) -- first buffer in list
    	while b ~= nil do
    		print(b.number, b.name, #b)
    		b = b:next()
    	end
    	vim.beep()
    	EOF
    	endfunction

    ==============================================================================

    4. Window userdata					*lua-window*

    Window objects represent vim windows. A window userdata "w" has the following
    properties and methods:

    Properties
    	o "w()" sets "w" as the current window.
    	o "w.buffer" contains the buffer of window "w" (read-only).
    	o "w.line" represents the cursor line position in window "w".
    	o "w.col" represents the cursor column position in window "w".
    	o "w.width" represents the width of window "w".
    	o "w.height" represents the height of window "w".

    Methods
    	o "w:next()" returns the window next to "w".
    	o "w:previous()" returns the window previous to "w".
    	o "w:isvalid()" returns 'true' (boolean) if window "w" corresponds to
    	    a "real" (not freed from memory) Vim window.

    Examples:

    	:lua w = vim.window() -- current window
    	:lua print(w.buffer.name, w.line, w.col)
    	:lua w.width = w.width + math.random(10)
    	:lua w.height = 2 * math.random() * w.height
    	:lua n,w = 0,vim.window(true) while w~=nil do n,w = n + 1,w:next() end
    	:lua print("There are " .. n .. " windows")

    ==============================================================================
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