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if_lua.txt    For Vim version 9.0.  Last change: 2021 Aug 06

                  VIM REFERENCE MANUAL    by Luis Carvalho

The Lua Interface to Vim                                lua Lua

1. Commands                     lua-commands
2. The vim module               lua-vim
3. List userdata                lua-list
4. Dict userdata                lua-dict
5. Blob userdata                lua-blob
6. Funcref userdata             lua-funcref
7. Buffer userdata              lua-buffer
8. Window userdata              lua-window
9. luaeval() Vim function       lua-luaeval
10. Dynamic loading             lua-dynamic

{only available when Vim was compiled with the +lua feature}

1. Commands                                             lua-commands

:[range]lua {chunk}
                        Execute Lua chunk {chunk}.


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

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

If [endmarker] is omitted from after the "<<", a dot '.' must be used after
{script}, like for the :append and :insert commands.  Refer to
:let-heredoc for more information.

This form of the :lua command is mainly useful for including Lua code
in Vim scripts.


        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))

To see what version of Lua you have:
        :lua print(_VERSION)

If you use LuaJIT you can also use this:
        :lua print(jit.version)

:[range]luado {body}    Execute Lua function "function (line, linenr) {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>, and the current line number.
                        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,$".


        :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

:[range]luafile {file}
                        Execute Lua script in {file}.
                        The whole argument is used as a single file name.


        :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. All Lua default libraries are available. 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.list([arg])         Returns an empty list or, if "arg" is a Lua
                                table with numeric keys 1, ..., n (a
                                "sequence"), returns a list l such that l[i] =
                                arg[i] for i = 1, ..., n (see List).
                                Non-numeric keys are not used to initialize
                                the list. See also lua-eval for conversion
                                rules. Example:
                                    :lua t = {math.pi, false, say = 'hi'}
                                    :echo luaeval('vim.list(t)')
                                    :" [3.141593, v:false], 'say' is ignored

        vim.dict([arg])         Returns an empty dictionary or, if "arg" is a
                                Lua table, returns a dict d such that d[k] =
                                arg[k] for all string keys k in "arg" (see
                                Dictionary). Number keys are converted to
                                strings. Keys that are not strings are not
                                used to initialize the dictionary. See also
                                lua-eval for conversion rules. Example:
                                    :lua t = {math.pi, false, say = 'hi'}
                                    :echo luaeval('vim.dict(t)')
                                    :" {'1': 3.141593, '2': v:false,
                                    :" 'say': 'hi'}

        vim.blob([arg])         Returns an empty blob or, if "arg" is a Lua
                                string, returns a blob b such that b is
                                equivalent to "arg" as a byte string.
                                    :lua s = "12ab\x00\x80\xfe\xff"
                                    :echo luaeval('vim.blob(s)')
                                    :" 0z31326162.0080FEFF

        vim.funcref({name})     Returns a Funcref to function {name} (see
                                Funcref). It is equivalent to Vim's

        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.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.type({arg})         Returns the type of {arg}. It is equivalent to
                                Lua's "type" function, but returns "list",
                                "dict", "funcref", "buffer", or "window" if
                                {arg} is a list, dictionary, funcref, buffer,
                                or window, respectively. Examples:
                                        :lua l = vim.list()
                                        :lua print(type(l), vim.type(l))
                                        :" list

        vim.command({cmds})     Executes one or more lines of Ex-mode commands
                                in {cmds}.
                                        :lua vim.command"set tw=60"
                                        :lua vim.command"normal ddp"
                                        lua << trim END
                                              new Myfile.js
                                              call search('start')

        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
                                userdata (see lua-list and lua-dict).
                                        :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.{fname})       Opens a new buffer for file {fname} and
                                returns it. Note that the buffer is not set as
                                current.{name} [, {args}])
                                Proxy to call Vim function named {name} with
                                arguments {args}.  Example:
                                        :lua print('has', 'timers'))

        vim.fn                  Proxy to call Vim functions. Proxy methods are
                                created on demand.  Example:
                                        :lua print(vim.fn.has('timers'))

        vim.lua_version         The Lua version Vim was compiled with, in the
                                form {major}.{minor}.{patch}, e.g. "5.1.4".

        vim.version()           Returns a Lua table with the Vim version.
                                The table will have the following keys:
                                        major - major Vim version.
                                        minor - minor Vim version.
                                        patch - latest patch included.

The Vim editor global dictionaries g: w: b: t: v: can be accessed
from Lua conveniently and idiomatically by referencing the vim.* Lua tables
described below. In this way you can easily read and modify global Vim script
variables from Lua.

Example: = 5     -- Set the g:foo Vim script variable.
    print(  -- Get and print the g:foo Vim script variable. = nil   -- Delete (:unlet) the Vim script variable.

vim.g                                                   vim.g
        Global (g:) editor variables.
        Key with no value returns nil.

vim.b                                                   vim.b
        Buffer-scoped (b:) variables for the current buffer.
        Invalid or unset key returns nil.

vim.w                                                   vim.w
        Window-scoped (w:) variables for the current window.
        Invalid or unset key returns nil.

vim.t                                                   vim.t
        Tabpage-scoped (t:) variables for the current tabpage.
        Invalid or unset key returns nil.

vim.v                                                   vim.v
        v: variables.
        Invalid or unset key returns nil.

3. List userdata                                        lua-list

List userdata represent vim lists, and the interface tries to follow closely
Vim's syntax for lists. Since lists are objects, changes in list references in
Lua are reflected in Vim and vice-versa. A list "l" has the following
properties and methods:

NOTE: In patch 8.2.1066 array indexes were changed from zero-based to
one-based.  You can check with:
            if has("patch-8.2.1066")

        o "#l" is the number of items in list "l", equivalent to "len(l)"
            in Vim.
        o "l[k]" returns the k-th item in "l"; "l" is one-indexed, as in Lua.
            To modify the k-th item, simply do "l[k] = newitem"; in
            particular, "l[k] = nil" removes the k-th item from "l". Item can
            be added to the end of the list by "l[#l + 1] = newitem"
        o "l()" returns an iterator for "l".
        o "table.insert(l, newitem)" inserts an item at the end of the list.
            (only Lua 5.3 and later)
        o "table.insert(l, position, newitem)" inserts an item at the
            specified position. "position" is one-indexed.  (only Lua 5.3 and
        o "table.remove(l, position)" removes an item at the specified
            position. "position" is one-indexed.

        o "l:add(item)" appends "item" to the end of "l".
        o "l:insert(item[, pos])" inserts "item" at (optional)
            position "pos" in the list. The default value for "pos" is 0.


        :let l = [1, 'item']
        :lua l = vim.eval('l') -- same 'l'
        :lua l:add(vim.list())
        :lua l[1] = math.pi
        :echo l[0] " 3.141593
        :lua l[1] = nil -- remove first item
        :lua l:insert(true, 1)
        :lua print(l, #l, l[1], l[2])
        :lua l[#l + 1] = 'value'
        :lua table.insert(l, 100)
        :lua table.insert(l, 2, 200)
        :lua table.remove(l, 1)
        :lua for item in l() do print(item) end

4. Dict userdata                                        lua-dict

Similarly to list userdata, dict userdata represent vim dictionaries; since
dictionaries are also objects, references are kept between Lua and Vim. A dict
"d" has the following properties:

        o "#d" is the number of items in dict "d", equivalent to "len(d)"
            in Vim.
        o "d.key" or "d['key']" returns the value at entry "key" in "d".
            To modify the entry at this key, simply do "d.key = newvalue"; in
            particular, "d.key = nil" removes the entry from "d".
        o "d()" returns an iterator for "d" and is equivalent to "items(d)" in


        :let d = {'n':10}
        :lua d = vim.eval('d') -- same 'd'
        :lua print(d, d.n, #d)
        :let d.self = d
        :lua for k, v in d() do print(d, k, v) end
        :lua d.x = math.pi
        :lua d.self = nil -- remove entry
        :echo d

5. Blob userdata                                        lua-blob

Blob userdata represent vim blobs. A blob "b" has the following properties:

        o "#b" is the length of blob "b", equivalent to "len(b)" in Vim.
        o "b[k]" returns the k-th item in "b"; "b" is zero-indexed, as in Vim.
            To modify the k-th item, simply do "b[k] = number"; in particular,
            "b[#b] = number" can append a byte to tail.

        o "b:add(bytes)" appends "bytes" to the end of "b".


        :let b = 0z001122
        :lua b = vim.eval('b') -- same 'b'
        :lua print(b, b[0], #b)
        :lua b[1] = 32
        :lua b[#b] = 0x33 -- append a byte to tail
        :lua b:add("\x80\x81\xfe\xff")
        :echo b

6. Funcref userdata                                     lua-funcref

Funcref userdata represent funcref variables in Vim. Funcrefs that were
defined with a "dict" attribute need to be obtained as a dictionary key
in order to have "self" properly assigned to the dictionary (see examples
below.) A funcref "f" has the following properties:

        o "#f" is the name of the function referenced by "f"
        o "f(...)" calls the function referenced by "f" (with arguments)


        :function I(x)
        :  return a:x
        :  endfunction
        :let R = function('I')
        :lua i1 = vim.funcref('I')
        :lua i2 = vim.eval('R')
        :lua print(#i1, #i2) -- both 'I'
        :lua print(i1, i2, #i2(i1) == #i1(i2))
        :function Mylen() dict
        :  return len(
        :  endfunction
        :let mydict = {'data': [0, 1, 2, 3]}
        :lua d = vim.eval('mydict'); d.len = vim.funcref('Mylen')
        :echo mydict.len()
        :lua l = d.len -- assign d as 'self'
        :lua print(l())

Lua functions and closures are automatically converted to a Vim Funcref and
can be accessed in Vim scripts.  Example:

        lua <<EOF
        vim.fn.timer_start(1000, function(timer)
            print('timer callback')

7. Buffer userdata                                      lua-buffer

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

        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 "" 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

        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
        o "b:isvalid()" returns 'true' (boolean) if buffer "b" corresponds to
            a "real" (not freed from memory) Vim buffer.


        :lua b = vim.buffer() -- current buffer
        :lua print(, 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"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)
                b = b:next()

8. Window userdata                                      lua-window

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

        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".

        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.


        :lua w = vim.window() -- current window
        :lua print(, 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")

9. luaeval() Vim function                               lua-luaeval lua-eval

The (dual) equivalent of "vim.eval" for passing Lua values to Vim is
"luaeval". "luaeval" takes an expression string and an optional argument and
returns the result of the expression. It is semantically equivalent in Lua to:

        local chunkheader = "local _A = select(1, ...) return "
        function luaeval (expstr, arg)
            local chunk = assert(loadstring(chunkheader .. expstr, "luaeval"))
            return chunk(arg) -- return typval

Note that "_A" receives the argument to "luaeval". Lua numbers, strings, and
list, dict, blob, and funcref userdata are converted to their Vim respective
types, while Lua booleans are converted to numbers. An error is thrown if
conversion of any of the remaining Lua types, including userdata other than
lists, dicts, blobs, and funcrefs, is attempted.


        :echo luaeval('math.pi')
        :lua a = vim.list():add('newlist')
        :let a = luaeval('a')
        :echo a[0] " 'newlist'
        :function Rand(x,y) " random uniform between x and y
        :  return luaeval('(_A.y-_A.x)*math.random()+_A.x', {'x':a:x,'y':a:y})
        :  endfunction
        :echo Rand(1,10)

10. Dynamic loading                                 lua-dynamic

On MS-Windows and Unix the Lua library can be loaded dynamically.  The
:version output then includes +lua/dyn.

This means that Vim will search for the Lua DLL or shared library file only
when needed.  When you don't use the Lua interface you don't need it, thus
you can use Vim without this file.


To use the Lua interface the Lua DLL must be in your search path.  In a
console window type "path" to see what directories are used.  The 'luadll'
option can be also used to specify the Lua DLL.  The version of the DLL must
match the Lua version Vim was compiled with.


The 'luadll' option can be used to specify the Lua shared library file instead
of DYNAMIC_LUA_DLL file what was specified at compile time.  The version of
the shared library must match the Lua version Vim was compiled with.