Background: pipeline architecture

[Paul Sandoz]

On Dec 31, 2012, at 10:11 PM, Brian Goetz <brian.goetz at Oracle.COM> wrote:
> The set of operations are defined in Stream for reference streams, and IntStream for int streams; each of these has a (private) implementation class {Reference,Int}Pipeline who share a (private) base class AbstractPipeline.  We represent a stream pipeline as a linked list of XxxPipeline objects, where each holds an op and links to its parent. Because of the shared base class, pipelines can cross shapes and still operations can be jammed together into a single pass, such as in:
> 
>  people.stream().filter(..).map(Person::getHeight).max();
>                 ^Stream<Person>
>                            ^Stream<Person>
>                                                   ^IntStream
> 
> and even though the "shape" of the data changes from reference to int we can create a single sink chain where we push Person objects in and (unboxed) ints come out.
> 

And this is how we could plug in a map stream in the future, either one that is sugar for a holding type or something more sophisticated in terms of storage and boxing avoidance of the keys and values.

Paul.