[stdpar][algorithms] Add support for unique_copy and unique
#1831
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@illuhad updated and ready 👍 |
illuhad
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Jul 23, 2025
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| auto pred = [first, p](auto x) { | ||
| auto input = x; | ||
| --input; |
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Is this well-defined if input is the first element?
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I think so, the if-condition on the next line checks for that case.
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Yes, but that's my question: Is it always well-defined to decrement any iterator below begin? Maybe the iterator behaves like an unsigned int and then encounters some underflow behavior or so which may be UB.
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This PR adds automatic offloading support for unique_copy and unique.
copy_ifinterface, although unique internally implements the same logic. This is because the lambda 'pred' needs to operate upon the iterator. Since incopy_ifthe predicate is called with a value, the interface is not readily usable forunique_copyanduniquealgorithms.