Generators (original) (raw)

Brian Goetz brian.goetz at oracle.com
Thu Jan 3 13:00:34 PST 2013

To be clear: range and ints() are the only remaining int generators?

Ranges: there's a "stepping" version of range too. And there will be long equivalents.

Repeating: there will be int versions of iterate/generate.

BigIntegers: This already works: Stream range = iterate(new BI(0), bi -> bi.plus(1))

but we could add something to BigInteger too.

There should be an iterator for stepping functions and infinite streams of 1's etc. ints() is nice anyway for samples and demos. I can't complain too much. Though the iterator form is pretty simple. I think ints() should wrap, just like the simple iterator implementation. Will the T generators allow us to generate streams of BigInteger? Those are useful for samples and demos. Generate a gazillion Fibonacci numbers.

On Thu, Jan 3, 2013 at 12:50 PM, Brian Goetz <brian.goetz at oracle.com_ _<mailto:brian.goetz at oracle.com>> wrote: Things like int sumOfFirstHundredPrimes = _ints().filter(isPrime()).limit(100).sum(); where you don't know how many input elements you'll have to examine.

On 1/3/2013 3:44 PM, Sam Pullara wrote: These look pretty reasonable to me. What is the motivation for ints()? Sam On Thu, Jan 3, 2013 at 11:49 AM, Brian Goetz <brian.goetz at oracle.com <mailto:brian.goetz at oracle.com> <mailto:brian.goetz at oracle.com_ _<mailto:brian.goetz at oracle.com>>> wrote:_ I'm looking over our generators. Currently we have: repeat(T) repeat(n, T) repeatedly(Supplier) repeatedly(n, Supplier) iterate(T, UnaryOperator) cycle(Iterable) I'd like to pare this down a lot. Paul and I have been discussing techniques for making limit() more efficient, at which point the first four can collapse to generate(Supplier) since you can simulate repeat(T) with generate(() -> T) and the limited versions with generate().limit(). That leaves us with iterate(T, UnaryOperator) cycle(Iterable) and I'm thinking cycle doesn't pull its weight either. If we took that out, we'd be down to the pleasantly small set of: generate(Supplier) iterate(T, UnaryOperator) For integer generators, we have range(from, to) and I think we should add ints() -> sugar for range(0, MAXINT) (Or should ints() be truly infinite, wrapping around?)

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