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Implement ExactSizeIterator for (Circular)TupleWindows #752

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Philippe-Cholet
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@Philippe-Cholet Philippe-Cholet commented Sep 18, 2023

Closes #660
Implement ExactSizeIterator without any additional cost:

  • For CircularTupleWindows by flattenning the struct Take<I> { iter: I, n: usize } from iter: Take<TupleWindows<Cycle<I>, T>> into iter: TupleWindows<Cycle<I>, T>, len: usize.
    It has the same length as the input (exact size) iterator.
    Implement FusedIterator as well.
  • For TupleWindows if the input iterator is exact sized. Relies on the fact that T::num_items() - 1 items are collected at definition.

Add a field to know the length of the iterator.
Implemented under the same conditions `Iterator` is implemented.
It implements a method `len` which rely on an exact size hint.
Implemented under the same conditions `Iterator` and `ExactSizeIterator` are implemented.
src/tuple_impl.rs Show resolved Hide resolved
`len` was a duplicate since `Take` also had it.
`CircularTupleWindows::next` is how is implemented `Take::next`.
@Philippe-Cholet Philippe-Cholet changed the title Implement ExactSizeIterator for CircularTupleWindows Implement ExactSizeIterator for (Circular)TupleWindows Sep 19, 2023
src/tuple_impl.rs Show resolved Hide resolved
@jswrenn jswrenn added this pull request to the merge queue Sep 19, 2023
Merged via the queue into rust-itertools:master with commit 882581f Sep 19, 2023
@Philippe-Cholet Philippe-Cholet deleted the circular-windows-exact-size branch September 19, 2023 13:36
@jswrenn jswrenn added this to the next milestone Sep 19, 2023
@jswrenn jswrenn mentioned this pull request Nov 14, 2023
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Implement ExactSizeIterator for CircularTupleWindows
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