limit and skip in StreamOps

[Brian Goetz]

Yep, already on the "to consider" list.  

On Aug 4, 2012, at 6:51 AM, Deepak S Patwardhan wrote:

> Hello,
> 
> Consider the following class which represents an infinite stream of natural
> numbers.
> 
> public class Naturals implements Streamable<Integer> {
> 
>    private int current = 1;
> 	
>    public Iterator<Integer> iterator() {
>        return new Iterator<Integer>() {
>            //.. hasNext() returns true
>            //.. remove is unsupported
> 
>            @Override public Integer next() {
>                return current ++;
>            }
>        };
>    }
> }
> 
> To compute the sum of first 5 numbers, I have to write
> 
> Stream<Integer> sumStream = naturals.cumulate((x, y) -> x + y);
> for (int i = 0; i < 4; i++) sumStream.next();
> int sum5 = sumStream.next();
> 
> Question 1) How about a (lazy) limit method in StreamOps which results in a
> sized stream? I can then write
> int sum5 = naturals.limit(5).reduce(0, (x, y) -> x + y);
> 
> Question 2) How about a (an eager) skip method in StreamOps which skips
> elements in the stream? I can then write
> int sum5 = naturals.cumulate((x, y) -> x + y).skip(4).next();
> 
> Although I have raised these in the context of infinite streams, I think
> they would apply to sized streams as well.
> 
> Regards,
> Deepak S Patwardhan.
> 
> 
>