Stream generators

[Brian Goetz]

> I don't think that infinite streams pull their weight,

Well, they don't weigh that much, either -- they don't introduce new 
concepts, they are just other ways to get a stream.  I think an integer 
range generator would be a reasonable minimum.

Many of the examples below can be synthesized from int ranges plus 
existing stream ops:

   intRange(...).map(e -> k)

The "repeatedly" sequences also can be easily synthesized:

   intRange(...).map(e -> supplier.get())


> I've had lab for 2 or 3 years where students play with with infinite
> iterators and lists,
> and it was always evaluated by student (our students grade labs, TA,
> profs etc.)
> as too difficult so the lab was eventually replaced.
>
> Rémi
>
> On 11/30/2012 06:21 PM, Brian Goetz 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)?
>>
>