P0429R9 A Standard flat_map #5626
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| \pnum | ||
| Any sequence container\iref{sequence.reqmts} \tcode{C} | ||
| supporting \oldconcept{RandomAccessIterator} can be used |
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This must be referring to C's associated iterator type(s). How can this be improved? For reference:
Any sequence container with random access iterator and supporting operations front(), push_back() and pop_back() can be used to instantiate priority_queue.
-- https://eel.is/c++draft/priority.queue#priqueue.overview-1.sentence-1
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@jwakely, @CaseyCarter: Any thoughts? I don't think this is broken enough to warrant an immediate fix here, but I'm happy to entertain editorial improvement requests.
Yes, there's a mess of interactions here. P2286 adds [assoc.format], the |
See the improved instructions in p2585r1, which is the version being polled at plenary. |
| -> flat_map<@\exposid{iter-key-type}@<InputIterator>, @\exposid{iter-mapped-type}@<InputIterator>, Compare>; | ||
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| template<ranges::input_range R, class Compare = less<@\exposid{range-key-type}@<R>>, | ||
| class Allocator> |
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Is this right? What does it mean that the previous template parameter Compare is defaulted, but Allocator isn't, even though both corresponding function parameters are defaulted? Seems like you can't get this to work without defaulting this Allocator: https://godbolt.org/z/fYesrsbMz.
| class Allocator> | |
| class Allocator = allocator<ranges::range_value_t<R>>> |
| class Allocator> | |
| class Allocator = allocator<@\exposid{range-mapped-type}@<R>>> |
I think both suggestions fulfill the corresponding Constraints element.
| class Allocator> | |
| class Allocator = allocator<void>> |
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I think allocator<void> would be just as good. It's going to be rebound anyway.
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@jwakely: are you (= LWG) happy to add a default argument allocator<void> here?
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I don't think that's editorial. Needs a library issue.
How about replacing them with |
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That would be correct, but I don't think it would improve the specification, as you have to follow an indirection to see what the constraint is actually telling you. Maybe that's OK, as the standard is not a tutorial. |
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- Replaced "may" with "can" in notes. - Replace && in constraints with prose "and" to avoid overfull \hbox
The earlier wording of "containers that the user defines" was not retained for new additions to the Standard, and it is needlessly informal. The term "program-defined" was only added recently, whereas the original wording has essentially existed since the beginnig.
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Fixes #5593
Fixes cplusplus/papers#101