SHEN: Erlang JavaScript Compiler

Simple

Libraries

We support following stack by Erlang JavaScript compiler:

• matches.js -- Erlang-like matching syntax
• tailrec.js -- optimize tail calls
• beacon.js -- FRP event streaming

The only real pratical fast solution is to translate Erlang AST into JavaScript using JavaScript helpers like matches.js and tailrec.js.

Usage

• Compilation to JavaScript, node.js, Browser, Client-Side FRP
• Macros, String Templates, Embedding Mode, Server-Side, N2O

Compilation to Pure JavaScript

In case of Client-Logic, Off-line clients, Client-side FRP Event System use can export you functions in module with -js attribute. All function will be stored to the same filename with js extension.

fac.erl:

    -module(fac).
    -compile({parse_transform, shen}).
    -compile(export_all).

    -js([start/0,fac/1]).

    start() ->
        N = fac(5),
        console:log("factorial ~p", [J, N]).

    fac(0) -> 1;
    fac(N) -> N * fac(N-1).

Compile with Erlang:

$ erlc shen.erl
$ erlc -pa . fac.erl

And you will get fac.js:

    var pattern = require("matches").pattern;
    var start = pattern({
        '': function() {
            j = 5;
            n = fac(j);
            return console.log('factorial ~p',[j,[n,[]]]);
    }});
    var fac = pattern({
        '0': function(x1) {
            return 1;
        },
        'n': function(n) {
            return n * fac(n - 1);
    }});
    start();

Now you can check:

$ node fac.js
factorial ~p [ 5, [ 120, [] ] ]

JavaScript Macros

Let say we want to generate JavaScript in our Erlang code which is very useful for Server-Logic Event System, so you can write programs in Erlang and expand them into JavaScript using -jsmacro attribute. Specified functions will be expanded to JavaScript during compilation.

    -module(fac).
    -compile({parse_transform, shen}).
    -compile(export_all).

    -jsmacro([macro/3]).

    macro(A,B,C) ->
        ws:send('Bert':encodebuf(
            [{source,'Bert':binary(A)},
             {x,C},
             {pickle,'Bert':binary(B)},
             {linked,C}])).

    main() ->
        A = "1",
        B = "2",
        Script = macro(A,B,"3"),
        io:format("JS Macro: ~s",[Script]).

Lets try it:

7> fac:main().
JS Macro: ws.send(Bert.encodebuf({source:Bert.binary(1),x:3,pickle:Bert.binary(2),linked:3}));
ok

Roadmap

1. multiple clauses for lambdas
2. list comprehensions
3. more JavaScript/OTP mappings
4. if statement :-)

Credits

* Maxim Sokhatsky
* Andrew Zadorozhny

OM A HUM