Stream generators

[Brian Goetz]

> I think it would be beneficial for comparison to show a bit of their
> implementations.

Here's iterate(seed, UnaryOperator):

     public static<T> Stream<T> iterate(final T seed, final 
UnaryOperator<T> f) {
         Objects.requireNonNull(f);
         final InfiniteIterator<T> iterator = new InfiniteIterator<T>() {
             T t = null;

             @Override
             public T next() {
                 return t = (t == null) ? seed : f.operate(t);
             }
         };
         return stream(new StreamSource.ForIterator<>(iterator), 
StreamOpFlag.IS_ORDERED);
     }

Not too difficult.  But, the idea is to make things that are easy in the 
header of a for-loop to be easy as the source of a stream.

> repeat(n) in Scheme is about 10 characters.

Yeah, well this is Java...

> How difficult is it to implement a merge, as might be needed to generate
> Hamming numbers? (One of my favorite test cases.)

You mean, interleave two streams?  That's on our list to implement as 
Streams.interleave(a, b).

> Is there a method to limit a stream to a length?  If so then one of your
> methods may be extra baggage.

Yes: stream.limit(n).