Mag is an optionally typed programming language with patterns, classes and multiple dispatch.

A simple Fibonacci function could look like this in Mag:

def fib(0) 0
def fib(1) 1
def fib(n Int) fib(n - 2) + fib(n - 1)

You can also implement this using a match statement:

def fib(n Int)
  match n
    case 0 then 0
    case 1 then 1
    case n then fib(n - 2) + fib(n - 1)
  end
end

As you can see, there are three method definitions with different arguments which share the same name. When the method named fib is called, the appropriate method body is chosen at runtime so that fib(0) returns 0, fib(1) returns 1 and fib(n) returns the Fibonacci number for any other input by calling itself recursively and calculating the result.

Mag is based on the Magpie language by Robert Nystrom, who is a language engineer at Google with a blog and a lot of amazing ideas. 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.