Forth in Javascript

Why?

I hear you ask why, which is hardly surprising.

• Forth was the first language I got good at
• Javascript is the language I like to play in now
• You can run it in any browser, and on a server, and on some embedded devices
• If its modular enough I should be able to replace the JS with C, C++, Wasm or Assembler.
• All the Forth I've seen has been really antiquated, or over-complex, needs a fresh approach

Installation

The only prerequisite is node and npm (or yarn).

npm install webforth

Installs webforth, note there are intentionally no dependencies in the minimal node or browser versions.

If you only want to host the web version, then cloning the git repo should be sufficient.

Running

const {Forth, ForthNodeExtensions} = require('webforth');

Or alternatively if running node v13, or node --experimental-modules

import {Forth, ForthNodeExtensions} from 'webforth';

Then ...

const foo = new Forth({extensions: ForthNodeExtensions);
foo.compileForthInForth()
  .then(() => foo.interpret('1 2 3 ROT .S')) // Pass forth to interpret
  .then(() => foo.console()) // Interactive console
  .catch((err) => console.log('Error',err));

This ...

• loads a bootstrap JS interpreter;
• loads forth into it;
• switches to the forth interpreter
• Starts a full forth console.

Try 1 2 3 ROT .S A simple forth command and output the stack

This is an experimental API - it might change,

• see any discussion in: issue#23.

In particular we'll be adding ability to load forth files into an instance.

Note, it should be possible to run multiple instances, but this isn't tested fully yet. e.g.

import {Forth, ForthNodeExtensions} from webforth;
const foo1 = new Forth({extensions: ForthNodeExtensions});
const foo2 = new Forth({extensions: ForthNodeExtensions});
foo2.compileForthInForth().then(() => foo2.console());
foo1.compileForthInForth().then(() => foo1.interpret('1 2 .S'));

Running in a browser

You should be able to run this at https://mitra.biz/forth/console.html

To make your own copy, clone the repo,

Start a simple http server such as that included in Node

cd webforth # Or wherever you cloned it
http-server &

Open http://localhost:8080/console.html in a browser.

The HTML uses Web Components and TextEncoders so they should work in any modern browsers such as: Firefox, Chrome, Opera, Edge, Android. It will not work in IE or Safari on IOS or OSX, and there are no plans to support those browsers, however I'll be happy to add PRs if someone else does.

It should compile Forth (you can verify in the web console) and present a console and entry box in which you can type any Forth.

Everything is happening locally i.e. this is forth running in your browser.

Debugging

For the browser version open the Console. The process of building the dictionary puts errors and progress there.

Feel free to open a new issue on the git repo but the first thing I'm going to ask for is a copy of whatever appeared in the Console, or in Node.

There are two useful Forth words you can insert in either a definition or the code to help debug.

• testing3: sets an internal flag to increase (significantly) debugging output so we see stack condition before every forth word. Changing debugDepth can be useful to get more or less of it. (look for the variable)
• break: Just calls a short routine that generates a console log, when working in my IDE I set a breakpoint here.

Arduino Support

Support for Arduino is just starting, so this might change!

The repo should ship with a working .ino, but to rebuild it:

• node --experimental-modules sandbox/example_dump.mjs
• Cut and paste from the output - look for the section commented at top and bottom as Arduino output
• Cut and paste into .ino - replacing the same section, which is currently the top of the file.

This will change to use an include file issue#59 and then to be output by the Web UI issue#61.

Contributing

Yes please !

Please introduce yourself on issue#1

Pull requests are welcome, and even quite significant changes at this stage, but lets discuss first (open a new issue in GIT).