Quick experiments with yielding effects in javascript

effects.js

function * get()  { return yield { label: "get", payload: null }; }
function * put(s) { return yield { label: "put", payload: s }; }

function * state(init, prog) {
  var s = init;
  var cmd = prog.next();
  while (!cmd.done) {
    switch (cmd.value.label) {
      case "get":
        cmd = prog.next(s);
        break;
      case "put":
        console.log(cmd);
        s   = cmd.value.payload;
        cmd = prog.next(null)
        break;
      default:
        cmd = prog.next(yield cmd.value);
    }
  }
  return cmd.value;
}


function * read() { return yield { label: "read", payload: null }; }

function * reader(init, prog) {
  var s = init;
  var cmd = prog.next();
  while (!cmd.done) {
    switch (cmd.value.label) {
      case "read":
        cmd = prog.next(s);
        s = s + 1;
        break;
      default:
        cmd = prog.next(yield cmd.value);
    }
  }
  return cmd.value;
}

function * example() {
  var x = yield * get();
  yield * put(4);
  var z1 = yield * read();
  var y  = yield * get();
  var z2 = yield * read();
  console.log(x, z1, z2, y)
}


// run the example
var p = state(1, reader(2, example()))
p.next();