Constructors 
- *fromArray: (arr : Array a) → Seq a* &mdash; Convert a JavaScript array into lazy sequence.
function fromArrayIter(arr, n) {
  if (n < arr.length) {
    return cons(arr[n], function () {
      return fromArrayIter(arr, n + 1);
    });
  } else {
    return nil;
  }
}