function generateOneof(generators) {
  // TODO: generator
  generators.forEach(function (gen) {
    assert(typeof gen === "function");
  });

  var result = generatorBless(function (size) {
    var idx = random(0, generators.length - 1);
    var gen = generators[idx];
    return gen(size);
  });

  return utils.curried2(result, arguments);
}
- `generator.oneof(gens: list (generator a)): generator a`