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Add C++20 iterators

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Reason: Requested on the mailing list.
This commit is contained in:
Gennaro Prota
2025-09-09 14:42:38 +02:00
parent 1b8ef09564
commit 35b0094529
5 changed files with 645 additions and 16 deletions
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doc/modules/ROOT/pages/index.adoc
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@@ -46,22 +46,12 @@ an unsigned long `n`, the bit at position `i` of the bitset has the same value
as `(n >> i) & 1`.
== Rationale
`dynamic_bitset` is not a <a
Because of the proxy reference type, `dynamic_bitset` is not a <a
href="https://en.cppreference.com/w/cpp/named_req/Container.html">Container</a>
and does not provide iterators for the following reason:
A container with a proxy reference type can not fulfill the container
requirements as specified in the C++ standard (unless one resorts to strange
iterator semantics). `std::vector<bool>` has a proxy reference type and does not
fulfill the container requirements and as a result has caused many problems. One
common problem is when people try to use iterators from `std::vector<bool>` with
a standard algorithm such as `std::search()`. The `std::search()` requirements
say that the iterator must be a LegacyForwardIterator, but
`std::vector<bool>::iterator` does not meet this requirement because of the
proxy reference. Depending on the implementation, they may or not be a compile
error or even a run-time error due to this misuse. For further discussion of the
problem see "Effective STL" by Scott Meyers. So `dynamic_bitset` tries to avoid
these problems by not pretending to be a container.
and its iterators do not satisfy the requirements for a LegacyForwardIterator.
This means that its iterators are not usable with many standard algorithms.
However, `dynamic_bitset` provides C++20 iterators which can be used with
ranges.
Some people prefer the name "toggle" to "flip". The name "flip" was chosen
because that is the name used in `std::bitset`. In fact, most of the function