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AnErlang/Elixir port for scripting application logic inLua. Works with Lua andLuaJIT.

Use Erlang...

{ok,Pid, []}=luaport:spawn(some_id,"path/to/scripts"),{ok, [6]}=luaport:call(Pid,multiply, [2,3]).

...or Elixir...

{:ok,pid,[]}=:luaport.spawn(:some_id,"path/to/scripts"){:ok,[6]}=:luaport.call(pid,:multiply,[2,3])

...to execute a Lua script.

functionmultiply(a,b)returna*bend

git clone https://github.com/asciibeats/luaport.gitcd luaportrebar3 ct

If you use Erlang andrebar3, add LuaPort as dependency to yourrebar.config.

{deps, [  {luaport,"~> 1.6"}]}.

Or for Elixir and mix, add it to yourmix.exs.

defpdepsdo[{:luaport,"~> 1.6"}]end

Create a Lua script atpath/to/scripts calledmain.lua.

functionsubtract(a,b)returna-bend

When using Erlang, don't forget to start the application.

application:start(luaport),{ok,Pid, []}=luaport:spawn(myid,"path/to/scripts"),{ok, [42]}=luaport:call(Pid,subtract, [43,1]),luaport:despawn(myid),application:stop(luaport).

With Elixir it will start automatically.

{:ok,pid,[]}=:luaport.spawn(:myid,"path/to/scripts"){:ok,[42]}=:luaport.call(pid,:subtract,[43,1]):luaport.despawn(:myid)

To return results on spawn and respawn, just add a return statement to yourmain.lua...

functiondo()print('something')endreturn23,42

...and retrieve them like this:

{ok,Pid1, [23,42]}=luaport:spawn(myid,"path/to/scripts"),{ok,Pid2, [23,42]}=luaport:respawn(myid).

To add static data to the port's context, add a map as third argument to the spawn function.

{ok,Pid, []}=luaport:spawn(myid,"path/to/scripts", #{config=> {what,ever},greeting=> <<"moin">>}).

The elements of that map will be available as global variables. Be careful not to choose colliding names, as these variables will be named after the maps keys.

locala,b=unpack(config)functiongreet()print(greeting)end

To push global variables into the context during runtime, use the push function.

luaport:push(myid, #{name=> <<"til">>}).

To pull dynamic data into the context, you may provide a callback module as the fourth argument to spawn.

{ok,Pid, []}=luaport:spawn(myid,"path/to/scripts", #{},callback).

-module(callback).-export([init/2,print/1]).init(String,Number)->  [#{string=>String},Number].print(Message)->io:format("Message:~p~n", [Message]).

Calls and casts will automagically be mapped to the module's function of the same name.

localmap,number=port.call.init('sunshine',49)port.cast.print('some message')

If you want to insert or just execute some code during runtime, use the load function.

{ok, []}=luaport:load(Pid, <<"function something() return 666 end">>),{ok, [666]}=luaport:call(Pid,something).

{ok, []}=luaport:load(Pid, <<"print('nice')">>).

{ok, [42]}=luaport:load(Pid, <<"return 42">>).

To be able to continuously call or cast functions after accidental or intended respawns, you could use{global, Name} or{local, Name} as reference to register the port.

{ok,Pid1, []}=luaport:spawn({local,myid},"path/to/scripts"),{ok,Pid2, []}=luaport:respawn({local,myid}),luaport:cast({local,myid},execute).

Requiring modules works normally. You may put a module.lua or module.so intopath/to/scripts or any other path in Lua's package.path or package.cpath, respectively.

localmodule=require('module')

Lua has no delayed call mechanism, therefore LuaPort provides an interface to Erlang's timer functions. The first argument is the time to wait in milliseconds.

localtref=port.after(3000,function (str)print(str)end,'call once, if not canceled')port.cancel(tref)

localtref=port.interval(1000,function (str)print(str)end,'call repeatedly until canceled')port.cancel(tref)

Finally, to just suspend execution for a while, use the sleep function.

port.sleep(2000)

Since Erlang and Lua datatypes do not align too nicely, there are some things to consider.

• Lua has only one collection type, the table. It is like a map in Erlang. So when maps get translated to Lua they become tables.
• When lists or tuples get translated they become tables with a metatype 'list' or 'tuple', respectively.
• Strings in Erlang are lists and translated as such. Lua has no dedicated binary type. If you want to translate to strings, use binary strings.
• Erlang has no boolean type and atoms serve no purpose in Lua context. So atom 'true' translates to true and atom 'false' to false.
• Atom 'nil' translates to nil.
• For convenience, all other atoms become strings. They will be handled like any other string on their way back.
• If compiled to useLuaJIT, LuaPort has no integer type. By default, numbers that arealmost integers get converted. You may modify this behaviour by definingLUAP_NOINT on compilation, disabling integer handling.
• LuaPort uses a custom print function mimicking Lua's own. It differs slightly: It shows its output in Erlang's shell and prints tables in depth.

• Apologies for the occasional poor commit discipline/hygiene.
• Thank you!