Adding bucket interface for std::deque?

[eulo...@live.com]

we have bucket interface for std::unordered_map. What about adding bucket interface for std::deque?

using local_iterator = implementation defined 

using const_local_iterator = implementation defined

begin(size_type) cbegin(size_type)	returns an iterator to the beginning of the specified bucket (public member function)
end(size_type) cend(size_type)	returns an iterator to the end of the specified bucket (public member function)
bucket_count	returns the number of buckets (public member function)
max_bucket_count	returns the maximum number of buckets (public member function)
bucket_size	returns the number of elements in specific bucket (public member function)
pointer data(size_type) const_pointer data(size_type) const	returns an pointer to the beginning of the specified bucket for passing C Interfaces

[Richard Smith]

On 19 October 2017 at 21:19, <eulo...@live.com> wrote:

we have bucket interface for std::unordered_map. What about adding bucket interface for std::deque?

Can you give some motivating examples where this would be valuable?

 

using local_iterator = implementation defined 

using const_local_iterator = implementation defined

begin(size_type) cbegin(size_type)	returns an iterator to the beginning of the specified bucket (public member function)
end(size_type) cend(size_type)	returns an iterator to the end of the specified bucket (public member function)
bucket_count	returns the number of buckets (public member function)
max_bucket_count	returns the maximum number of buckets (public member function)
bucket_size	returns the number of elements in specific bucket (public member function)
pointer data(size_type) const_pointer data(size_type) const	returns an pointer to the beginning of the specified bucket for passing C Interfaces

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[Nicol Bolas]

On Friday, October 20, 2017 at 12:19:54 AM UTC-4, ejsvifq mabmip wrote:

we have bucket interface for std::unordered_map. What about adding bucket interface for std::deque?

To have a "bucket interface", you need to first have the idea that buckets exist at all.

Unordered containers have bucket interfaces because they have buckets as a first-class concept. There are ways to control how many buckets exist and so forth. This is not the case for a `deque`. The number of buckets is essentially an accident of the implementation. For example, if the number of items per bucket in an implementation is 10, and you put 12 elements in a `deque`, how many buckets are there? Well, it could be as many as 3, depending on how you inserted them.

Equally importantly, how would that even work? Which bucket is referred to by index 0? If you insert a bunch of items at the beginning, is index 0 still referring to the same bucket anymore? Remember: a `deque` is a "double-ended queue"; the whole point of the type is that insertion/removal from the ends doesn't affect iteration. There's pretty much no way to provide that with so-called bucket iterators.