A prototype implementation of the Mμl multi-method programming language, as described in the paper "Mμl: The Power of Dynamic Multi-Methods", presented at the Workshop on Meta-Programming Techniques and Reflection (META’19).

Instructions:

1. Install racket
2. install brag (using raco pkg install brag)
3. Run racket paper-code.mμl (or run racket on any other Mμl file)
4. Wait for your code to finish running, the implementation is quite slow, so be patient!

Files:

0. multi-methods.pdf: the paper.
1. compiler.rkt: a "compiler" that can be used with rackets #lang directive, it will lex, parse and desugar a Mμl file into an AST, that is then wrappep into racket code, that when executed will parse the Mμl ast to our redex implementation (see below).
2. grammar.rkt: the production rules for the grammar (written in brag)
3. runtime.rkt: the "runtime", a straightforward implementation of our reduction rules, written in PLT Redex.
4. paper-code.mμl: all the Mμl code in the paper, together with checks that expressions produce the correct values.

Syntax:

The syntax is as shown in the paper, in addition:

• The first line of your file must be #lang reader "compiler.rkt"
• An identifier must start with a unicode letter, and can contain any number of extra letters, numbers or -s
• A string literal cannot contain any double quotation marks ("s), and does not recognise any escape sequences
• A single-line comment starts with // and ends at the next newline (a newline must be before the end of file)
• A multi-line comment starts with /* and ends at the next occurence */ (they do not nest)
• Any Unicode whitespace characters are ignored and only serve to sperate tokens.
• The entire file must be an expression, in particular, it must not end in a semicolon, or be empty.