Stream generators

[Joe Bowbeer]

My first impression is that there are a lot. Whether they carry their
weight depends on how difficult it is to implement these directly.

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

repeat(n) in Scheme is about 10 characters.

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

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

Joe
On Nov 30, 2012 9:21 AM, "Brian Goetz" <brian.goetz at oracle.com> wrote:

> We've got a few generators for infinite streams already implemented. For
> object streams:
>
>   // produces seed, f(seed), f(f(seed)), ...
>   <T> iterate(T seed, UnaryOperator<T> f)
>
>   // infinite constant sequence
>   <T> repeat(T t)
>
>   // finite constant sequence
>   <T> repeat(int n, T t)
>
>   // infinite sequence driven by a supplier function
>   <T> repeatedly(Supplier<T> f)
>
>   // finite sequence driven by a supplier function
>   <T> repeatedly(int n, Supplier<T> f)
>
>   // infinitely cycle through an Iterable
>   <T> cycle(Iterable<T> iterable)
>
> For integer streams, the above, plus
>
>   range(int from, int to)
>   range(int from, int to, int step)
>
>
> Ignoring naming for the time being:
>
>  - Do these carry their weight?
>  - Are we missing any?
>  - What related functionality are we missing that might undermine the
> utility of these (e.g., zip)?
>
>