neovim/runtime/doc/if_lua.txt

*if_lua.txt*    For Neovim


		  VIM REFERENCE MANUAL    by Luis Carvalho


The Lua Interface to Vim				*lua* *Lua*

1. Commands			|lua-commands|
2. The vim module		|lua-vim|
3. The luaeval function		|lua-luaeval|

==============================================================================
1. Commands						*lua-commands*

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

Examples:
>
	:lua vim.api.nvim_command('echo "Hello, Neovim!"')
<

:[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.api.nvim_win_get_cursor(0)[1]
	local curline = vim.api.nvim_buf_get_lines(
		0, linenr, linenr + 1, false)[1]
	print(string.format("Current line [%d] has %d bytes",
		linenr, #curline))
	EOF
	endfunction

Note that in example variables are prefixed with local: they will disappear 
when block finishes. This is not the case for globals.

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

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

							*:luado*
:[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,$".
							{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. 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 Neovim
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. Currently it only has `api` 
submodule which is a table with all API functions. Descriptions of these 
functions may be found in |api-funcs.txt|.

==============================================================================
3. The luaeval function					*lua-luaeval* *lua-eval*
							*luaeval()*

The (dual) equivalent of "vim.eval" for passing Lua values to Vim is
"luaeval". "luaeval" takes an expression string and an optional argument used 
for _A inside expression 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
	end

Note that "_A" receives the argument to "luaeval". Lua nils, numbers, strings, 
tables and booleans are converted to their Vim respective types. An error is 
thrown if conversion of any of the remaining Lua types is attempted.

Note 2: lua tables are used as both dictionaries and lists, thus making it 
impossible to determine whether empty table is meant to be empty list or empty 
dictionary. Additionally lua does not have integer numbers. To distinguish 
between these cases there is the following agreement:

0. Empty table is empty list.
1. Table with N incrementally growing integral numbers, starting from 1 and 
   ending with N is considered to be a list.
2. Table with string keys, none of which contains NUL byte, is considered to 
   be a dictionary.
3. Table with string keys, at least one of which contains NUL byte, is also 
   considered to be a dictionary, but this time it is converted to 
   a |msgpack-special-map|.
4. Table with `vim.type_idx` key may be a dictionary, a list or floating-point 
   value:
   - `{[vim.type_idx]=vim.types.float, [vim.val_idx]=1}` is converted to 
     a floating-point 1.0. Note that by default integral lua numbers are 
     converted to |Number|s, non-integral are converted to |Float|s. This 
     variant allows integral |Float|s.
   - `{[vim.type_idx]=vim.types.dictionary}` is converted to an empty 
     dictionary, `{[vim.type_idx]=vim.types.dictionary, [42]=1, a=2}` is 
     converted to a dictionary `{'a': 42}`: non-string keys are ignored. 
     Without `vim.type_idx` key tables with keys not fitting in 1., 2. or 3. 
     are errors.
   - `{[vim.type_idx]=vim.types.list}` is converted to an empty list. As well 
     as `{[vim.type_idx]=vim.types.list, [42]=1}`: integral keys that do not 
     form a 1-step sequence from 1 to N are ignored, as well as all 
     non-integral keys.

Examples: >

	:echo luaeval('math.pi')
	: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)

Note that currently second argument to `luaeval` undergoes VimL to lua 
conversion, so changing containers in lua do not affect values in VimL. Return 
value is also always converted. When converting, |msgpack-special-dict|s are 
treated specially.

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