afternoon-lang

Please read before poking at the code.

I read the anecdote about Arthur Whitney writing an interpreter fragment for the J language in an afternoon, and thought it would make for a good challenge to kill some time. The essay itself is here. The idea of the challenge was pretty much: given 24 hours, write a programming language from scratch.

The language I tried to write in a span of 24 hours (albeit it ended more around 16-18ish hours due to various life constraints) is in lang.c. A few notes on the code:

1. No documentation, one single file. Pretty difficult to read as I didn't intend on going back to read it ever, I was purely interested in writing a quick and dirty implementation to optimize for time.
2. Lots of shortcuts are taken. Various macros are used to do a lot of things.
3. No memory is released. No garbage collection. Just shooting with a ton of allocations.
4. Features not implemented for time: maps half implemented (parsing, but no runtime support). Control flow statements (if/while/for/foreach).
5. Riddled with bugs, issues, and, errors. Don't expect much from it - I was mostly focused on adding things into it rather than debugging current issues since time was of the essence.
6. I tried to separate out the code into 3 chunks, the lexer, the parser, and, the runtime.
7. Theres a lot of very strangely named variables/types/macros. A lot of especially around types, as theres about 3 sets of them in there for various things (tokens/ast nodes/runtime).
8. In my sample "spec" (hardly would consider it one though) below, I use ":object", however in the parser this is mostly referred to as :map (however it never made it to the runtime).

This is far, far, from decent code that I would ever want to build on or work with, but for a little self-challenge I'm happy with where it turned out for that short period of time. I don't intend to ever touch the source base again, but it was definitely fun to hack on for a bit.

Compiling & Running

If you're interested in seeing the result, I compiled with the following command:

$ gcc lang.c -o lang

As well it can be ran ./lang to run in REPL mode, or ./lang test.sl to run the example source.

Samples

NOTE: this was in a file called spec.md I wrote in the first few minutes of starting

I'm just going to write a bunch of ideas down and hopefully it comes together into a cohesive language.

let var1 :number = 0;
let var2 :string = "asdf";
let var3 :list[:string] = [ "test", var2 ];
let var4 :object[:string, :string] = { "test" => var1 };
let fn4 :function[:number, :number, :number] = function (a :number, b :number) :number {
    return a + b;    
};

reserved tokens

• number
• string
• list
• object
• function