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README.md

Egg.js - A Smalltalk VM that runs on top of JavaScript

In a nutshell, here you get a bunch of js files that allow how to load an image file in a JSON format and execute Smalltalk code by evaluating Egg code.

IMPORTANT NOTE this is heavily w.i.p and there are quite a few things that may not work.

Getting Started

If you want the typical image and VM files, you can just download an eggjs release from the appropriate section in github. Else you can build the whole thing, y

Building

Running make js from root egg dir should build everything needed

Build system

The idea is that you have egg code in root dir, and here in image-segments subdir you'll get the binaries for the parts of the image, like kernel.json and compiler.json.

A bootstrap process generates those files from bare egg code, using pharo (see egg/bootstrap/pharo). The process of bootstrapping does the following (it's all done automatically through make):

1 - generates a bootstrap pharo image, with the needed pharo code, where it is possible to create a little virtual egg image from egg sources 2 - loads the Powerlang-* packages using Iceberg 3 - executes JSTranspiler transpileEggInterpreter to generate the js files of the interpreter. Those files get writen egg/runtimes/js/interpreter. 4 - executes JSTranspiler generateKernelModule et al

Running the code

There are different ways in which you could run Egg code in a JS platform. You could run it on top of node.js or inside a web browser. We started by supporting running on top of node.js.

Exploring a Smalltalk image that runs on top of nodejs

This creates a small webserver that loads an egg image and responds webside requests, so that you can browse and debug it remotely:

## clone and enter the main dir for js platform
$ git clone git@github.com:powerlang/egg.git
$ cd egg/runtime/js

## first install webside server dependencies
$ cd webside && npm install && cd .. 

## Now run the server
$ node example-server/index.js

## Now connect from a webside client to address http://localhost:9005/

Using Smalltalk as a library from nodejs

For this example, let's look at runtime/js/example-bench.

// bench.js
import { performance } from "perf_hooks"; // nodejs built-in for measuring time
import Egg from '../Egg.js';

var egg = new Egg();
egg.loadKernelFile("Kernel.json");

let n1 = 1, t1;
do {
    let startTime = performance.now();
    egg.send(egg.runtime.newInteger_(n1), "benchSieve");
    let endTime = performance.now();
    t1 = endTime - startTime;
    if (t1 >= 1000) break;
    n1 = n1 * 2;
} while (true)

let n2 = 28, t2, r;
do {
    let startTime = performance.now();
    r = egg.send(egg.runtime.newInteger_(n2), "benchFibonacci").value();
    let endTime = performance.now();
    t2 = endTime - startTime;
    if (t2 >= 1000) break;
    n2 = n2 + 1;
} while (true)

console.log(`${(n1 * 500000.0 * 1000 / t1).toFixed()} bytecodes/sec; ${(r * 1000.0 / t2).toFixed()} sends/sec`)

You can run it with the following lines:

$ node example-bench/bench.js
1242848 bytecodes/sec; 95553 sends/sec

Using egg as a node module (not yet implemented)

npm install egg-js

## Opening a Smalltalk REPL
$ node repl.js
Welcome to egg.js!
[1] > 3 + 4
7
[2] > q
See you soon!
$

Using Smalltalk as a library in a web page (not yet implemented)

# bench.html
<!DOCTYPE html>
<html>
  <head>
    <script src="https://cdn.jsdelivr.net/npm/powerlang/dist/egg.js">
    <script>
      const runtime = egg.launch();
      const result = egg.evalExpression("(3 + 4) printString");
      document.body.appendChild(result.toLocalString());
    </script>
    <title>egg.js in action</title>
  </head>
  <body>
  </body>
</html>

System overview - A.K.A. how egg.js works

To run Smalltalk code you need a Smalltalk image and a Smalltalk evaluator (usually an interpreter). To run it on top of JavaScript the interpreter needs to be made of JavaScript code.

Instead of writing the evaluator directly in JavaScript, in egg.js we take Egg/Pharo evaluator, written in Smalltalk, and transpile its sources to JavaScript.

For the Smalltalk image, again we use Egg/Pharo, this time to bootstrap a virtual Smalltalk kernel image from sources, and then to make that kernel write an image file tailored for the web, in JSON format.

Both the JSON image and JS interpreter are generated using the Makefile. The image will be created in image-segments folder and the interpreter is written in interpreter folder.

Additionally, the repo contains some glue JS code in st-glue.js to support the evaluator, debugging and launching the image.