Lua
is an ergonomic interface to Luerl, aiming to be the best way to use Luerl from Elixir.
~LUA
sigil for validating Lua code at compile-timedeflua
macro for exposing Elixir functions to Lua- Improved error messages and sandboxing
- Deep setting/getting variables and state
- Excellent documentation and guides for working with Luerl
When referring to this library,
Lua
will be stylized as a link.References to Lua the language will be in plaintext and not linked.
Lua
can be run using the eval!/2
function
iex> {[4], _} =
...> Lua.eval!(~LUA"""
...> return 2 + 2
...> """)
The simplest way to expose an Elixir function to Lua is using the Lua.set!/3
function
lua =
Lua.set!(Lua.new(), [:sum], fn args ->
[Enum.sum(args)]
end)
{[10], _} = Lua.eval!(lua, ~LUA"return sum(1, 2, 3, 4)"c)
For easily expressing APIs, Lua
provides the deflua
macro for exposing Elixir functions to Lua
defmodule MyAPI do
use Lua.API
deflua double(v), do: 2 * v
end
lua = Lua.new() |> Lua.load_api(MyAPI)
{[10], _} =
Lua.eval!(lua, ~LUA"""
return double(5)
""")
Lua
can be used to expose complex functions written in Elixir. In some cases, you may want to call Lua functions from Elixir. This can
be achieved with the Lua.call_function!/3
function
defmodule MyAPI do
use Lua.API, scope: "example"
deflua foo(value), state do
Lua.call_function!(state, [:string, :lower], [value])
end
end
lua = Lua.new() |> Lua.load_api(MyAPI)
{["wow"], _} = Lua.eval!(lua, ~LUA"return example.foo(\"WOW\")")
You can also use Lua
to modify the state of the lua environment inside your Elixir code. Imagine you have a queue module that you
want to implement in Elixir, with the queue stored in a global variable
defmodule Queue do
use Lua.API, scope: "q"
deflua push(v), state do
# Pull out the global variable "my_queue" from lua
queue = Lua.get!(state, [:my_queue])
# Call the Lua function table.insert(table, value)
{[], state} = Lua.call_function!(state, [:table, :insert], [queue, v])
# Return the modified lua state with no return values
{[], state}
end
end
lua = Lua.new() |> Lua.load_api(Queue)
{[queue], _} =
Lua.eval!(lua, """
my_queue = {}
q.push("first")
q.push("second")
return my_queue
""")
["first", "second"] = Lua.Table.as_list(queue)
Lua
piggy-backs off of Robert Virding's Luerl project, which implements a Lua lexer, parser, and full-blown Lua virtual machine that runs inside the BEAM.