What is Elang?

Elang is a a Python-like language for the Emacs VM.

It is a Frankenstein’s monster, created using a ported Python tokenizer, a Python subset parser and a compiler which emits Emacs VM byte-code.

How to play with it?

Install the names package.

Clone the repository, add the resulting directory to your load-path and do (require 'elang).

Then open one of the example files in the examples/ directory and do, say, (elang-eval-current-defun) while having the point somewhere within one of the test functions there.

The function should become available through M-: or any other means of running Emacs Lisp functions.

Check the examples/ directory for code that should work now.

Alternatively, Elang is also available on MELPA (see the elang package), although I still recommend doing it manually.

How does it work?

What do you think? It tokenizes (see elang-tokenizer.el) the code, parses (elang-parser.el) the token stream, then compiles (elang-compiler.el) the parse tree to a byte-compiled Emacs function and executes the latter.

To load a complete file it just parses the file, finding def’s and global assignments, loading the functions and setting global variables.

Note that global assignments currently do not evaluate it’s values.

Who needs such a beast?

In it’s current state - nobody, as there’s just too much to do for me. This is something I created just to see if Emacs VM can be a target for a language different from Lisps. And it turns out it can..! I believe this prototype can be turned into something quite useful, or interesting at least.

So see TODO.org for a list of things currently missing, and don’t hesitate to ask questions or offer code improvements!

Gotchas

Actually, only the most basic things currently work, i.e. expressions and funcalls. Things to remember additionally:

1. This is not Python. This is not even a port of the language. Technically this is Emacs Lisp using basic Python syntax ideas.
2. The language uses dynamic binding.
3. The language does not interoperate with Emacs Lisp in a nice way, i.e. there’s no was to deal with symbols, or declare an interactive function.
4. No list or map-related syntax.