gistfile1.js

  function wu(thing) {
    return new wu.Iterable(thing);
  }

  // This is known as @@iterator in the ES6 spec. Until it is bound to some
  // well-known name or importable, find the @@iterator object by expecting it
  // as the first property accessed on a for-of iterable.
  //
  // This shim is thanks to @andywingo via @gozala.
  const iteratorSymbol = (function() {
    try {
      for (let _ of Proxy.create({get: function(_, name) { throw name; } }))
        break;
    } catch (name) {
      return name;
    }
    throw new Error("Cannot find iterator symbol.");
  }());

  function makeIterator(thing) {
    if (thing[iteratorSymbol]) {
      return thing[iteratorSymbol];
    }
    if (typeof thing == "number") {
      return wu.range(0, thing)[iteratorSymbol];
    }
    if (typeof thing == "object" && thing !== null) {
      return TODO
    }
    throw new Error("Not iterable: " + thing);
  }

  wu.Iterable = function (thing) {
    this[iteratorSymbol] = Function.isGenerator(thing)
      ? thing
      : makeIterator(thing);
  };