# Introduction
Mag is an optionally typed, object-oriented programming language with patterns, classes and multimethods.
A simple example showing some code for a (very inefficent) recursive Fibonacci function can be defined like this using multimethods:
```python
def fib(0) 0
def fib(1) 1
def fib(n Int) fib(n - 2) + fib(n - 1)
```
This defines the same `fib` method multiple times, which is okay since the method signatures differ between the implementations, replacing the need for a separate conditional check inside the function.
More documentation will follow in the future, and make sure to check out [Robert Nystrom's blog posts about Magpie](https://journal.stuffwithstuff.com/category/magpie/) for further information. His posts serve as the foundational inspiration for this project.
# Features
### Extensibility
The parser and compiler structures use a modular, trait-based architecture with structs which handle the actual translation, which means that the actual interpretation of semantics is dynamic and may be extended by Mag code at runtime using [a special parselet](https://journal.stuffwithstuff.com/2011/02/13/extending-syntax-from-within-a-language/), a concept which could even be extended to compilation and execution to provide a very flexible programming environment.
### Pattern Matching
Patterns are not just used in Rust-like `match` expresions, they are actually dispersed throughout the whole language fabric of `mag` and `magc`, where it is used for method arguments, variable destructuring, error reporting and many other useful things.
# Getting Started
Enough fuzzy talk, let's start a REPL from the command line to get this project up and running.
Run the following command from the project root to start the REPL:
```
cargo run
```
Try to enter simple arithmetic expressions like `1 + 2` or `3 * 7` to see the execution pipeline in action. Expect a lot of bugs for now!
## Credits
Mag is based on the Magpie language by [Robert Nystrom](http://stuffwithstuff.com/), who is a language engineer at Google with [a blog and a lot of amazing ideas](http://journal.stuffwithstuff.com/category/magpie/). His various blog posts are what started and inspired this project, and I plan on continuing his legacy even if the original codebase ceases further development.
However, since there are a few syntactical differences to the original Magpie language, the two languages are *source-incompatible* and thus have different names. In particular, Bob's implementation substitutes the dot commonly used for calling methods on objects with a space (usually a meaningless character), which I find rather unintuitive, especially for new programmers.