Lox (clox) is an object-oriented scripting language developed alongside the reading of craftinginterpreters (craftinginterpreters.com) by Bob Nystrom.

I've followed along, but added my own features as well.

• Multi-threading with libpthread and a global VM lock. Threads can run concurrently for IO and other blocking operations, but cannot run concurrently in the VM itself (like cpython and cruby).
• try/catch exception handling
• Splatted (rest) parameters and arguments
• Map (hash/dict) literals
• Regular expressions
• Default arguments
• Keyword arguments
• Mutable strings
• Modules similar to Ruby's
• Blocks similar to Ruby's
• Iterators and foreach() statement
• Integrated REPL
• String interpolation
• Multi-process support using fork() syscall
• Signal handling: registering signal handlers, sending signals
• Small standard library
• Object finalizers

• creation of AST before compilation phase (separate parser/compiler)
• bytecode optimization passes (including constant folding)
• Generational M&S garbage collector with managed heaps

• Standard library networking support
• Support string methods that work on utf8 codepoints
• Add constants (no redefinitions, will given compiler or runtime error)
• See TODO for more info
• Add JIT compiler, either method or tracing

• Only tested on linux (Ubuntu 16.04) and mac OS, uses fork() and libpthread, as well as some C99 features
• Tested with gcc and clang
• Almost C++ compliant (g++ compiles, clang++ doesn't)

Here's an example from the standard library:

class Benchmark {
  class start(name: "Benchmark", iterations: 10) {
    var times = [];
    print "Running ${iterations} iterations";
    for (var i = 0; i < iterations; i+=1) {
      var t1 = Timer();
      yield();
      var t2 = Timer();
      times << (t2 - t1);
    }
    this.report(name, iterations, times);
  }

  class report(name, iters, times) {
    print "============";
    print name;
    print "============";
    print "Iterations: ${iters}";
    var sum = 0;
    for (var i = 0; i < times.size(); i+=1) {
      sum += times[i].seconds();
    }
    var avg = sum/times.size();
    print "Average iteration (s): ${avg}";
  }
}

// Usage:

fun bench() {
  for (var i = 0; i < 100000; i+=1) {
    [1,2,3,4,5] << 1;
  }
}

Benchmark.start(name: "array", iterations: 1, &bench);

See the examples folder for more examples, and the lib folder for the standard library. The files in the examples folder are also tests run by the ./bin/test_examples binary (see Makefile for more details).

Thanks to Bob Nystrom for the book and github repo!