Lioness • Cub • SavannaKit

The Cub Programming Language

Cub is an interpreted, dynamically typed, scripting language inspired by Swift. This project includes a lexer, parser, compiler and interpreter, all written in Swift.

Cub is used for OpenTerm's scripting feature. A language guide is available in OpenTerm and online. Cub was derived from Lioness (my first programming language).

The standard library (abbreviated: stdlib) contains basic utility functions, for example to convert from/to dates.

Source examples

The following Cub code calculates factorials recursively:

func factorial(x) returns {
	
    if x > 1 {
        return x * factorial(x - 1)
    }
	
    return 1
}

a = factorial(5) // a = 120

The following Cub code uses a do times loop:

a = 1
n = 10
do n times {
    a += a
}
// a = 1024

More examples can be found here.

External functions

An important feature Cub has is the ability to define external functions. These functions are implemented in native code (for example Swift) and thus allows Cub to call native code.

An external function pauses the interpreter, executes the native code, and resumes the interpreter when the native code is executed.

The following example implements a print function:

let runner = Runner(logDebug: true, logTime: true)
		
runner.registerExternalFunction(name: "print", argumentNames: ["input"], returns: true) { (arguments, callback) in
			
	for (name, arg) in arguments {
		print(arg)
	}
			
	callback(nil)
}

External functions are called like any other global functions in Cub, the print function from the example above could be called like this:

print("Hello world")

Features

Minimalistic, yet expressive, syntax
No type system, language is dynamic
5 basic operators: +, -, /, * and ^
- ^ means "to the power of", e.g. 2^10 equals 1024
- all operators have a shorthand, e.g. += for +
Numbers
- All numbers are floating point
Booleans
- Can be evaluated from comparison
- Can be defined by literal: true or false
Strings
- Can be concatenated with the + operator
Arrays
- Can contain any type, including other arrays
Functions
- Supports parameters, returning and recursion
- Can be declared inside other functions
Structs
- Can contain any type, including other structs
Loops
- for
- while
- do times
- repeat while
- break
- continue
if / else / else if statements

Running

Since the project does not rely on any dependencies, running it requires no setup.

macOS

Open Cub.xcworkspace (preferably in the latest non-beta version of Xcode) and run the macOS Example target. The example will run the code in A.cub. The output will be printed to the console.

Installing framework

Using Swift Package Manager

Add to your Package.swift file's dependencies section:

.Package(url: "https://github.com/louisdh/cub.git",
		         majorVersion: 1, minor: 0)

Using CocoaPods

Add the following line to your Podfile:

pod 'Cub', '~> 1.0'

Using Carthage

Add the following line to your Cartfile:

github "louisdh/cub" ~> 1.0

Run carthage update to build the framework and drag the built Cub.framework into your Xcode project.

Roadmap

Xcode file template

Cub source files can easily be created with Xcode, see XcodeTemplate.md for instructions.

Architecture

A detailed explanation of the project's architecture can be found here.

License

This project is available under the MIT license. See the LICENSE file for more info.