FusionScript

The programming language of ultimate dankliness

Note: I will no longer be actively working on FusionScript. I have decided that I should make better use of my time instead of working on a proof of concept that I don't expect anyone to use. The code will remain available but will most likely not be updated for future versions of Lua and new features will not be added.

Warning: This project is very unstable and possibly has many bugs. If your code does not compile, it is very likely a problem in the compiler or a change in the language instead of your code. Please feel free to add an issue if any errors arise that you believe were caused by the compiler.

What is FusionScript?

FusionScript is a language that runs on the Lua runtime (currently, by transpiling to Lua and then using a Lua interpreter) inspired by C++, Python, and Lua. Eventually, FusionScript will compile to a modified Lua 5.3 bytecode and run on a modified Lua VM.

FusionScript offers an improved runtime type checking system (that checks between both native Lua types, as well as instances of a class) by using the standard library's assert.is() method. Eventually, runtime type checking may be implemented using syntax similar to Pythonic type hints and checked using bytecode instructions.

FusionScript also has a class system, with the ability to inherit values from a superclass as well as an "interface" system that when used (see below) will ensure that classes implement certain methods. Below is an example that closely mirrors the standard library's scope module:

interface IScope { descope; with; }
class Scope {
	with(fn)=> {
		fn(self);
	}
}

-- Example:

local lfs = require("lfs");

class UseDir extends Scope implements IScope {
	descope()=> lfs.chdir(@old_dir);
	__init(directory)=> {
		@old_dir = lfs.currentdir();
		@dir = directory;
		lfs.chdir(directory);
	}
}

UseDir("/tmp"):with(\=> {
	File("thing.txt"):with(\file-> {
		file:write("Hello World!\n");
	});
});

There is also implemented an easier way to use generators / iterators using the async and yield functions:

async gen_numbers(low = 1, high)->
	for (i=low, high)
		yield i;

for (number in gen_numbers(1, 10))
	print(number);

Commands

fusion-ast: Compile a file into an abstract syntax tree (AST).

This program will load a file and print out a syntax tree for the file. The program will generate a syntax error and exit with error code 1 if a file has a syntax error.

fusion-pkg: Install and manage FusionScript packages

The fusion-pkg program offers a very simple wrapper around Git that offers the ability to use Git URLs as well as GitHub repositories to clone a repo and a simple way to upgrade all locally installed repos. The repos will be placed in the vendor folder, which is automatically searched when require() is invoked. There's two subcommands for fusion-pkg:

get - Clone a GitHub url (pattern user/repository) or a Git url, pattern (git+<url>).

upgrade - Upgrade a locally installed package.

remove - Remove a locally installed package; url is the repository name.

fusion: Run FusionScript files

The fusion program (which at the current time is an alias to fusion-source) can load syntaxes from .fuse files, compile them, and run them. As of 02-12-2016, compiled syntax trees are not cached. In future releases, either the syntax trees or the compiled Lua output might be cached to allow faster responsiveness when loading a program.

fusion-source: Run FusionScript with the Lua VM

The fusion-source program compiles FusionScript files at runtime and runs them using the same Lua VM. This means that running fusion-source will NOT produce the same output as fusionc-source then running the generated file with lua. This could leave undesired side effects from lpeg, fusion,, and luafilesystem libraries. However, the libraries themselves should not edit the global state and only remain in the package table.

There are two command line flags that can be used with the fusion-source program:

--package - Load the main module of the supplied package argument and exit. This is somewhat similar to the Python -m flag.

--metadata - Load the metadata module of the supplied package argument and print out the compatible information. Acceptable fields are documented here.

The fusion-source interpreter also makes it so the using keyword isn't required for loading syntax extensions. If the target audience for a script is intended to not use fusionc-source to compile to Lua, it is suggested to not use the using keyword.

fusionc: Compile FusionScript

The fusionc will use whatever alias is currently in place as the compiler. Use the documentation for the alias instead of this one to learn more about how the compiler works. The default compiler as of 01-12-2016 is fusionc-source.

fusionc-source: Compile FusionScript to Lua

The fusionc-source compiler can take FusionScript files and compile them to formatted Lua source. Because the compilation is from source to source, some things may look awkwardly formatted when compiled. As of 01-12-2016, there is no way to automatically compile FusionScript code to Lua bytecode.

There's a single command line flag that allows the output of the parser to be printed to the standard output, which is -p.

Examples

Hello World

print("Hello World!\n");

Factorial

factorial(n)->
    if (== n 0)
        return 1;
    else
        return (* n factorial((- n 1)));

print(tostring(factorial(5)));

Account (from Lua Demo)

class Account {
    __new(balance = 0)=> {
        @balance = balance;
    }

    deposit(amount)=> {
        @balance = (+ @balance amount);
        return true;
    }

    withdraw(amount)=> {
        if (> amount @balance)
            return false;
        else {
            @balance = (- @balance amount);
            return true;
        }
    }

    balance()=>
        return @balance;
}

bob = Account(500); -- 500
bob:deposit(600);   -- 1100
bob:withdraw(1000); -- 100
assert(bob:withdraw(math.max)); -- errors

Building

luarocks make --local