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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.

Trill is not to be confused with Microsoft/Trill, an engine for streaming data processing.


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.


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.

Building and Using

Trill builds on macOS and Linux using CMake. We have a convenient build script that obviates the need for using CMake directly. Once you've got LLVM and CMake installed, you'll need to generate pkgconfig files for LLVM and Clang -- we have a tool for this in the utils directory. You'll only need to run it once.

utils/build --pkgconfig

To install the build script dependencies:

pip install pkgconfig
pip install git+

Then, you should be able to run our build script. Just running the build script gets you a build of trill in the .build/debug folder.

usage: build [-h] [--swift SWIFT] [-r RELEASE] [-x] [-t]

optional arguments:
  -h, --help            show this help message and exit
  --swift SWIFT         Path to custom swift executable.
  -r RELEASE, --release RELEASE
                        Build the executable in the Release configuration
  -x, --xcodeproj       Build an Xcode project for the trill compiler.
  -t, --test            Run the trill test suite.

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.
  • There is no garbage collection / automatic reference counting, so allocated trill types will leak like crazy.
  • 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.


Harlan Haskins (@harlanhaskins) Samuel Giddins (@segiddins) Robert Widmann (@codafi)


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


A type safe, compiled language inspired by (and written in) Swift







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