How many floating-point numbers are in the interval [0,1]? (2017)

Re:How many floating-point numbers are in the interval [0,1]... by flerchin on Sunday April 16, 2023 @05:00PM (#35594227)

It's not clear to me how the streams api did it, but it's clear to me now that the count of a range of integers is just the end minus the start. This is a fast operation, and I'm not sure if it was performed at compile time, by the JIT, or as a specification of the streams api.

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Re:How many floating-point numbers are in the interval [0,1]... by SpaghettiCthulu on Sunday April 23, 2023 @09:47AM (#35676211)

The optimization is done in the JDK implementation (math shortcut) and then further taken advantage of by the JIT (inlining and constant folding).

How is this done?

The implementation of a `Spliterator` that is used internally by `IntStream.rangeClosed` overrides the `estimateSize` method to return `((long) upTo) - from + last`, and the `characteristics` method to return, among others, the `Spliterator.SIZED` characteristic. That characteristic indicates that `estimateSize` can be trusted to be exact, and when present, `estimateSize` will be used as a shortcut in the implementation of `Stream.count`, which can be seen in `ReduceOps.makeRefCounting`.

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