*lua-dict*
2. Table with string keys, none of which contains NUL byte, is a dict.
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|.
                                                             *lua-special-tbl*
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.array}` is converted to an empty list. As well
     as `{[vim.type_idx]=vim.types.array, [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: >vim

    :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: Second argument to `luaeval` is converted ("marshalled") from Vimscript
to Lua, so changes to Lua containers do not affect values in Vimscript. Return
value is also always converted. When converting, |msgpack-special-dict|s are
treated specially.

==============================================================================
Vimscript v:lua interface                                         *v:lua-call*

From Vimscript the special `v:lua` prefix can be used to call Lua functions
which are global or accessible from global tables. The expression >vim
    call v:lua.func(arg1, arg2)
is equivalent to the Lua chunk >lua
    return func(...)
where the args are converted to Lua values. The expression >vim
    call v:lua.somemod.func(args)
is equivalent to the Lua chunk >lua
    return somemod.func(...)

Lua module functions can be accessed like: >vim
    call v:lua.require'mypack'.func(arg1, arg2)
    call v:lua.require'mypack.submod'.func(arg1, arg2)
Note: Only single quote form without parens is allowed. Using
`require"mypack"` or `require('mypack')` as a prefix does NOT work.

You can use `v:lua` in "func" options like 'tagfunc', 'omnifunc', etc.
For example consider the following Lua omnifunc handler: >lua

    function mymod.omnifunc(findstart, base)
      if findstart == 1 then
        return 0
      else
        return {'stuff', 'steam', 'strange things'}
      end
    end
    -- Note: The module ("mymod") must be a Lua global, or use require() as
    -- shown above to access it from a package.
    vim.bo[buf].omnifunc = 'v:lua.mymod.omnifunc'

You can also use `v:lua` to call Lua functions as Vimscript |method|s: >vim
    :eval arg1->v:lua.somemod.func(arg2)
<
Note: `v:lua` without a call is not allowed in a Vimscript expression:
|Funcref|s cannot represent Lua functions. The following are errors: >vim

    let g:Myvar = v:lua.myfunc        " Error
    call SomeFunc(v:lua.mycallback)   " Error
    let g:foo = v:lua                 " Error
    let g:foo = v:['lua']             " Error
<
==============================================================================
Lua standard modules                                              *lua-stdlib*

The Nvim Lua "standard library" (stdlib) is the `vim` module, which exposes
various functions and sub-modules. It is always loaded, thus `require("vim")`
is unnecessary.

You can peek at the module properties: >vim

    :lua vim.print(vim)

Result is something like this: >

    {
      _os_proc_children = <function 1>,