Trill

Trill is a simple, type-safe, compiled programming language. Partially inspired by Swift, Trill has most simple language features one would expect (functions, structures, pointers) and some more high-level language features, like types with methods, garbage collected types, overloading, tuples/multiple returns, and closures.

Why did you make this?

Really, it's an exercise to learn compiler design, code generation to LLVM, and how to make a language that's actually fun to write.

Example

The following program finds the n th Fibonacci number:

func fib(_ n: Int) -> Int {
  var previous = 0
  var current = 1
  for var i = 0; i < n; i += 1 {
    let tmp = previous
    previous = current
    current = previous + tmp
  }
  return current
}

func main() {
  printf("%d\n", fib(10)) // prints 89
}

See the examples folder for more examples of Trill’s language features.

Backends

Trill has two backends, one for LLVM IR, and one for JavaScript. The JavaScript backend does not accurately represent the semantics of Trill, and really only exists to provide very simple interpreting of Trill programs inside the iOS app.

LLVM IR

The main backend for Trill is LLVM. It uses LLVM and Clang’s C APIs to call into LLVM’s code generation and clang importing features from within Swift. It currently makes a best effort to import all supported declarations from the C standard library headers as foreign declarations, ready for use in Trill.

iOS App

This repo also contains an iOS app that will perform semantic syntax highlighting, error reporting, and timing information for Trill. It will also convert Trill to JavaScript and execute it live on the device.

When using Trill in a JavaScript context, you can forward-declare certain types and methods that exist within the JavaScript standard library and use them from Trill as you would from JavaScript. Trill will ensure that your types are matched up, then emit the equivalent dynamic JavaScript.

foreign type Date {
  foreign func unixTimestamp() -> Int
  func getTime() -> Int {
    return self.unixTimestamp() / 1_000
  }
}

func main() {
  println(Date().getTime())
}

Building and Using

Trill currently is only supported on macOS, with the following dependencies:

LLVMSwift and TinyGC, which are vendored as git submodules. Run git submodule update --init to clone them.
LLVM's libraries. Install them with brew install llvm.

To build and create Trill programs, you need to open the Xcode project and build the trill scheme.

Outstanding issues

Closures are entirely unsupported in the LLVM backend. Closures are very much still in progress.
There are no generics. I’m working on a protocol-based generics system that uses runtime boxes with type metadata.
There are no enum s, like in Swift. enums from C are currently imported as global constants
There is a very limited standard library that exists alongside libc. You pretty much just get whatever you get with C, which includes all the pitfalls of manual pointers.
- Ideally I have a standard library that vends common types like Array , String , Dictionary , Set , etc.
The LLVM codegen is definitely not optimal, and certainly not correct.
Many more yet-unknown issues and corner-cases.

Should I use Trill in production?

Absolutely not. Trill is still in very early development, and is much more of a toy than anything serious. Everything is subject to change without any notice at all.

Author

Harlan Haskins (@harlanhaskins)

License

Trill is released under the terms of the MIT license, a copy of which is included in this repository.

sairamkotha/trill