Koka Zero

Reimplementation of core Koka, compiling to LLVM-IR, for my third-year dissertation.

This uses Algebraic Subtyping rather than Koka's Hindley-Milner inference with effect rows, since the former can give a precise effect to each subexpression of a program, which enables some optimisations.

Try Koka Zero in the language playground.

Example (a generator producing the Fibonacci sequence)

effect control yield-int(x : int) : ();

// yield the fibonacci numbers
fun fibs() {
  fun fibs-from(current, next) {
    yield-int(current);
    fibs-from(next, current + next);
  };
  fibs-from(0, 1);
}

fun main() {
  with control yield-int(n) {
    // print the fibonacci numbers below 100
    if n <= 100
    then {
      print-int(n);
      resume(());  // keep generating
    }else { 
      ();  // stop generating
    };
  };
  fibs();
}
// outputs: 0 1 1 2 3 5 8 13 21 34 55 89

Setup

Requirements:

• opam the OCaml package manager
• LLVM toolchain including clang
• optional: libgc - the Boehm Garbage Collector

# creates a fresh opam switch to install ocaml & the project's dependencies
make switch
make install-deps  
make build

Configuation

koka-zero-config.sexp points to the compilation dependencies which aren't captured by opam. These should be updated to point to the current install of clang, the runtime.c file within this project, and libgc. The latter is Boehm Garbage Collector, linked against for memory management. To compile without garbage collection, set (gc_path ()).

Usage

The compiler binary is in bin/main.exe - compile.sh is a wrapper that calls it with the koka-zero-config.sexp.

./compile.sh samples/reader.kk
./reader

Or run the interpreter with:

make start -- interpret samples/fib.kk

Running the Tests

make test