Add StreamExt::scan #2044
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Add StreamExt::scan #2044
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taiki-e
reviewed
Jan 20, 2020
cramertj
reviewed
Jan 21, 2020
| /// ``` | ||
| fn scan<S, B, Fut, F>(self, initial_state: S, f: F) -> Scan<Self, S, Fut, F> | ||
| where | ||
| F: FnMut(&mut S, Self::Item) -> Fut, |
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There isn't a way to fix this at the moment, sadly, but this is subtly the wrong method signature for this function, because it doesn't allow Fut to hold onto &mut S. There's no way to fix this right now due to limitations of HRTBs / GATs, so I don't mind accepting this PR now, but note that this makes this API dramatically less useful than it could be otherwise.
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Thanks for the PR! If you have time to send a PR to add documentation about the restriction I listed above, that'd be perfect, but no worries if not! |
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This PR adds combinator similar to https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.scan.
It may be useful for some cases when it's needed to cut stream or transform one stream into another using some state-based computations.