Make CoalesceBy lazy #801
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Make CoalesceBy lazy #801
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In order to make `DedupByWithCount` lazy soon, I first need to be able to make `|v| (1, v)` more generic.
Similar to what is done by `core::iter::Peekable`, a nested option is now used.
This behavior is not obvious at first glance of `Iterator::next`. In it, after `let init =`, `last` is `Some(None)` in both cases. With `try_fold`, if `iter` is not exhausted then we have `*last = Some(Some(..))` (otherwise it remains `Some(None)`).
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jswrenn approved these changes Nov 25, 2023
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Related to #792
To make the
CoalesceByadaptor lazy, I use a nested option again.This would make methods
coalesceanddedup[_by][_with_count]all lazy.But it required some preliminary adaptation because of
last: iter.next().map(|v| (1, v)),indedup_by_with_countfunction. Make this lazy required to delay|v| (1, v). And I therefore created structsNoCountandWithCountsharing a same behavior with the newCountItemtrait.Let me know what you think about it.