// bslstl_set.h                                                       -*-C++-*-
#ifndef INCLUDED_BSLSTL_SET
#define INCLUDED_BSLSTL_SET

#include <bsls_ident.h>
BSLS_IDENT("$Id: $")

//@PURPOSE: Provide an STL-compliant set class.
//
//@CLASSES:
//   bsl::set: STL-compatible set template
//
//@CANONICAL_HEADER: bsl_set.h
//
//@SEE_ALSO: bslstl_multiset, bslstl_map
//
//@DESCRIPTION: This component defines a single class template `bsl::set`,
// implementing the standard container holding an ordered sequence of unique
// keys.
//
// An instantiation of `set` is an allocator-aware, value-semantic type whose
// salient attributes are its size (number of keys) and the ordered sequence of
// keys the `set` contains.  If `set` is instantiated with a key type that is
// not itself value-semantic, then it will not retain all of its value-semantic
// qualities.  In particular, if the key type cannot be tested for equality,
// then a set containing that type cannot be tested for equality.  It is even
// possible to instantiate `set` with a key type that does not have a
// copy-constructor, in which case the `set` will not be copyable.
//
// A set meets the requirements of an associative container with bidirectional
// iterators in the C++ standard [23.2.4].  The `set` implemented here adheres
// to the C++11 standard when compiled with a C++11 compiler, and makes the
// best approximation when compiled with a C++03 compiler.  In particular, for
// C++03 we emulate move semantics, but limit forwarding (in `emplace`) to
// `const` lvalues, and make no effort to emulate `noexcept` or
// initializer-lists.
//
///Requirements on `KEY`
///---------------------
// A `set` is a fully "Value-Semantic Type" (see {`bsldoc_glossary`}) only if
// the supplied `KEY` template parameters is fully value-semantic.  It is
// possible to instantiate a `set` with `KEY` parameter arguments that do not
// provide a full set of value-semantic operations, but then some methods of
// the container may not be instantiable.  The following terminology, adopted
// from the C++11 standard, is used in the function documentation of `set` to
// describe a function's requirements for the `KEY` template parameter.  These
// terms are also defined in section [17.6.3.1] of the C++11 standard.  Note
// that, in the context of a `set` instantiation, the requirements apply
// specifically to the set's entry type, `value_type`, which is an alias for
// `KEY`.
//
///Glossary
///--------
// ```
// Legend
// ------
// 'X'    - denotes an allocator-aware container type (e.g., 'set')
// 'T'    - 'value_type' associated with 'X'
// 'A'    - type of the allocator used by 'X'
// 'm'    - lvalue of type 'A' (allocator)
// 'p',   - address ('T *') of uninitialized storage for a 'T' within an 'X'
// 'rv'   - rvalue of type (non-'const') 'T'
// 'v'    - rvalue or lvalue of type (possibly 'const') 'T'
// 'args' - 0 or more arguments
// ```
// The following terms are used to more precisely specify the requirements on
// template parameter types in function-level documentation.
//
//: *default-insertable*: `T` has a default constructor.  More precisely, `T`
//:   is `default-insertable` into `X` means that the following expression is
//:   well-formed:
//:   `allocator_traits<A>::construct(m, p)`
//:
//: *move-insertable*: `T` provides a constructor that takes an rvalue of type
//:   (non-`const`) `T`.  More precisely, `T` is `move-insertable` into `X`
//:   means that the following expression is well-formed:
//:   `allocator_traits<A>::construct(m, p, rv)`
//:
//: *copy-insertable*: `T` provides a constructor that takes an lvalue or
//:   rvalue of type (possibly `const`) `T`.  More precisely, `T` is
//:   `copy-insertable` into `X` means that the following expression is
//:   well-formed:
//:   `allocator_traits<A>::construct(m, p, v)`
//:
//: *move-assignable*: `T` provides an assignment operator that takes an rvalue
//:   of type (non-`const`) `T`.
//:
//: *copy-assignable*: `T` provides an assignment operator that takes an lvalue
//:   or rvalue of type (possibly `const`) `T`.
//:
//: *emplace-constructible*: `T` is `emplace-constructible` into `X` from
//:   `args` means that the following expression is well-formed:
//:   `allocator_traits<A>::construct(m, p, args)`
//:
//: *erasable*: `T` provides a destructor.  More precisely, `T` is `erasable`
//:   from `X` means that the following expression is well-formed:
//:   `allocator_traits<A>::destroy(m, p)`
//:
//: *equality-comparable*: The type provides an equality-comparison operator
//:   that defines an equivalence relationship and is both reflexive and
//:   transitive.
//
///Memory Allocation
///-----------------
// The type supplied as a set's `ALLOCATOR` template parameter determines how
// that set will allocate memory.  The `set` template supports allocators
// meeting the requirements of the C++11 standard [17.6.3.5], in addition it
// supports scoped-allocators derived from the `bslma::Allocator` memory
// allocation protocol.  Clients intending to use `bslma` style allocators
// should use the template's default `ALLOCATOR` type: The default type for
// the `ALLOCATOR` template parameter, `bsl::allocator`, provides a C++11
// standard-compatible adapter for a `bslma::Allocator` object.
//
///`bslma`-Style Allocators
/// - - - - - - - - - - - -
// If the (template parameter) type `ALLOCATOR` of a `set` instantiation' is
// `bsl::allocator`, then objects of that set type will conform to the standard
// behavior of a `bslma`-allocator-enabled type.  Such a set accepts an
// optional `bslma::Allocator` argument at construction.  If the address of a
// `bslma::Allocator` object is explicitly supplied at construction, it is used
// to supply memory for the set throughout its lifetime; otherwise, the set
// will use the default allocator installed at the time of the set's
// construction (see `bslma_default`).  In addition to directly allocating
// memory from the indicated `bslma::Allocator`, a set supplies that
// allocator's address to the constructors of contained objects of the
// (template parameter) type `KEY` with the `bslma::UsesBslmaAllocator` trait.
//
///Operations
///----------
// This section describes the run-time complexity of operations on instances
// of `set`:
// ```
// Legend
// ------
// 'K'             - (template parameter) type 'KEY' of the set
// 'a', 'b'        - two distinct objects of type 'set<K>'
// 'rv'            - modifiable rvalue of type 'set<K>'
// 'n', 'm'        - number of elements in 'a' and 'b' respectively
// 'c'             - comparator providing an ordering for objects of type 'K'
// 'al             - an STL-style memory allocator
// 'rg'            - range of objects convertible to 'value_type`
// 'i1', 'i2'      - two iterators defining a sequence of 'value_type' objects
// 'k'             - an object of type 'K'
// 'rk'            - modifiable rvalue of type 'K'
// 'p1', 'p2'      - two 'const' iterators belonging to 'a'
// distance(i1,i2) - the number of elements in the range [i1, i2)
//
// +----------------------------------------------------+--------------------+
// | Operation                                          | Complexity         |
// +====================================================+====================+
// | set<K> a;    (default construction)                | O[1]               |
// | set<K> a(al);                                      |                    |
// | set<K> a(c, al);                                   |                    |
// +----------------------------------------------------+--------------------+
// | set<K> a(rv); (move construction)                  | O[1] if 'a' and    |
// | set<K> a(rv, al);                                  | 'rv' use the same  |
// |                                                    | allocator,         |
// |                                                    | O[n] otherwise     |
// +----------------------------------------------------+--------------------+
// | set<K> a(b); (copy construction)                   | O[n]               |
// | set<K> a(b, al);                                   |                    |
// +----------------------------------------------------+--------------------+
// | set<K> a(i1, i2);                                  | O[N] if [i1, i2)   |
// | set<K> a(i1, i2, al);                              | is sorted with     |
// | set<K> a(i1, i2, c, al);                           | 'a.value_comp()',  |
// |                                                    | O[N * log(N)]      |
// |                                                    | otherwise, where N |
// |                                                    | is distance(i1,i2) |
// +----------------------------------------------------+--------------------+
// | set<K> a(from_range, rg);                          | O[N] if 'rg' is    |
// | set<K> a(from_range, rg, al);                      | sorted with        |
// | set<K> a(from_range, rg, c, al);                   | 'a.value_comp()',  |
// |                                                    | O[N * log(N)]      |
// |                                                    | otherwise, where N |
// |                                                    | is ranges::        |
// |                                                    |       distance(rg) |
// +----------------------------------------------------+--------------------+
// | a.~set<K>(); (destruction)                         | O[n]               |
// +----------------------------------------------------+--------------------+
// | a = rv;      (move assignment)                     | O[1] if 'a' and    |
// |                                                    | 'rv' use the same  |
// |                                                    | allocator,         |
// |                                                    | O[n] otherwise     |
// +----------------------------------------------------+--------------------+
// | a = b;       (copy assignment)                     | O[n]               |
// +----------------------------------------------------+--------------------+
// | a.begin(), a.end(), a.cbegin(), a.cend(),          | O[1]               |
// | a.rbegin(), a.rend(), a.crbegin(), a.crend()       |                    |
// +----------------------------------------------------+--------------------+
// | a == b, a != b                                     | O[n]               |
// +----------------------------------------------------+--------------------+
// | a < b, a <= b, a > b, a >= b                       | O[n]               |
// +----------------------------------------------------+--------------------+
// | a.swap(b), swap(a, b)                              | O[1] if 'a' and    |
// |                                                    | 'b' use the same   |
// |                                                    | allocator,         |
// |                                                    | O[n + m] otherwise |
// +----------------------------------------------------+--------------------+
// | a.size()                                           | O[1]               |
// +----------------------------------------------------+--------------------+
// | a.max_size()                                       | O[1]               |
// +----------------------------------------------------+--------------------+
// | a.empty()                                          | O[1]               |
// +----------------------------------------------------+--------------------+
// | get_allocator()                                    | O[1]               |
// +----------------------------------------------------+--------------------+
// | a.insert(k)                                        | O[log(n)]          |
// | a.insert(rk)                                       |                    |
// | a.emplace(Args&&...)                               |                    |
// +----------------------------------------------------+--------------------+
// | a.insert(p1, k)                                    | amortized constant |
// | a.insert(p1, rk)                                   | if the value is    |
// | a.emplace(p1, Args&&...)                           | inserted right     |
// |                                                    | before p1,         |
// |                                                    | O[log(n)]          |
// |                                                    | otherwise          |
// +----------------------------------------------------+--------------------+
// | a.insert(i1, i2)                                   | O[log(N) *         |
// |                                                    |   distance(i1,i2)] |
// |                                                    |                    |
// |                                                    | where N is         |
// |                                                    | n + distance(i1,i2)|
// +----------------------------------------------------+--------------------+
// | a.insert_range(rg)                                 | O[log(N) *         |
// |                                                    |  ranges::          |
// |                                                    |      distance(rg)] |
// |                                                    |                    |
// |                                                    | where N is  n +    |
// |                                                    | ranges::           |
// |                                                    |        distance(rg)|
// +----------------------------------------------------+--------------------+
// | a.erase(p1)                                        | amortized constant |
// +----------------------------------------------------+--------------------+
// | a.erase(k)                                         | O[log(n) +         |
// |                                                    | a.count(k)]        |
// +----------------------------------------------------+--------------------+
// | a.erase(p1, p2)                                    | O[log(n) +         |
// |                                                    | distance(p1, p2)]  |
// +----------------------------------------------------+--------------------+
// | a.erase(p1, p2)                                    | O[log(n) +         |
// |                                                    | distance(p1, p2)]  |
// +----------------------------------------------------+--------------------+
// | a.clear()                                          | O[n]               |
// +----------------------------------------------------+--------------------+
// | a.key_comp()                                       | O[1]               |
// +----------------------------------------------------+--------------------+
// | a.value_comp()                                     | O[1]               |
// +----------------------------------------------------+--------------------+
// | a.contains(k)                                      | O[log(n)]          |
// +----------------------------------------------------+--------------------+
// | a.find(k)                                          | O[log(n)]          |
// +----------------------------------------------------+--------------------+
// | a.count(k)                                         | O[log(n) +         |
// |                                                    | a.count(k)]        |
// +----------------------------------------------------+--------------------+
// | a.lower_bound(k)                                   | O[log(n)]          |
// +----------------------------------------------------+--------------------+
// | a.upper_bound(k)                                   | O[log(n)]          |
// +----------------------------------------------------+--------------------+
// | a.equal_range(k)                                   | O[log(n)]          |
// +----------------------------------------------------+--------------------+
// ```
//
///Usage
///-----
// In this section we show intended use of this component.
//
///Example 1: Creating a Holiday Calendar
/// - - - - - - - - - - - - - - - - - - -
// In this example, we will utilize `bsl::set` to define and implement a class,
// `HolidayCalendar`, that provides a calendar that allows client to add and
// remove holiday dates and determine whether a particular date is a holiday.
//
// First, we define and implement the methods of a value-semantic type,
// `MyDate`, that represents a date: (Note that for brevity, we do not
// explicitly document the invariants of a valid date.)
// ```
// /// This class implements a value-semantic attribute class
// /// characterizing a date according to the (Gregorian) Unix date
// /// convention.
// class MyDate {
//
//     // DATA
//     int d_year;
//     int d_month;
//     int d_day;
//
//   public:
//     // CREATORS
//
//     /// Create a `MyDate` object having the value represented by the
//     /// specified `year`, `month`, and `day`.  The behavior is undefined
//     /// unless the value represented by `year`, `month`, and `day` is
//     /// valid.
//     MyDate(int year, int month, int day)
//     : d_year(year), d_month(month), d_day(day)
//     {
//     }
//
//     /// Create a `MyDate` object having the same value as the specified
//     /// `original` object.
//     MyDate(const MyDate& original)
//     : d_year(original.d_year)
//     , d_month(original.d_month)
//     , d_day(original.d_day)
//     {
//     }
//
//     /// Destroy this object
//     //! ~MyDate() = default;
//
//     // MANIPULATORS
//
//     /// Assign to this object the value of the specified `rhs` object,
//     /// and return a reference providing modifiable access to this
//     /// object.
//     MyDate& operator=(const MyDate& rhs)
//     {
//         d_year = rhs.d_year;
//         d_month = rhs.d_month;
//         d_day = rhs.d_day;
//         return *this;
//     }
//
//     // ACCESSORS
//
//     /// Return the year of this date.
//     int year() const
//     {
//         return d_year;
//     }
//
//     /// Return the month of this date.
//     int month() const
//     {
//         return d_month;
//     }
//
//     /// Return the day of this date.
//     int day() const
//     {
//         return d_day;
//     }
//
// };
//
// // FREE FUNCTIONS
//
// /// Return `true` if the specified `lhs` and `rhs` objects have the same
// /// value, and `false` otherwise.  Two `MyDate` objects have the same
// /// value if each of their corresponding `year`, `month`, and `day`
// /// attributes respective have the same value.
// inline
// bool operator==(const MyDate& lhs, const MyDate& rhs)
// {
//     return lhs.year()  == rhs.year() &&
//            lhs.month() == rhs.month() &&
//            lhs.day()   == rhs.day();
// }
//
// /// Return `true` if the specified `lhs` and `rhs` objects do not have
// /// the same value, and `false` otherwise.  Two `MyDate` objects do not
// /// have the same value if each of their corresponding `year`, `month`,
// /// and `day` attributes respective do not have the same value.
// inline
// bool operator!=(const MyDate& lhs, const MyDate& rhs)
// {
//     return !(lhs == rhs);
// }
// ```
// Then, we define a comparison functor for `MyDate` objects in order for them
// to be stored in a `bsl::set` object:
// ```
// /// This `struct` defines an ordering on `MyDate` objects, allowing them
// /// to be included in associative containers such as `bsl::set`.
// struct MyDateLess {
//
//     /// Return `true` if the value of the specified `lhs` is less than
//     /// (ordered before) the value of the specified `rhs`, and `false`
//     /// otherwise.  The `lhs` value is considered less than the `rhs`
//     /// value if the date represented by `lhs` is earlier than the date
//     /// represented by `rhs` in time.
//     bool operator() (const MyDate& lhs, const MyDate& rhs) const
//     {
//         if (lhs.year() < rhs.year()) return true;
//         if (lhs.year() == rhs.year()) {
//             if (lhs.month() < rhs.month()) return true;
//             if (lhs.month() == rhs.month()) {
//                 if (lhs.day() < rhs.day()) return true;
//             }
//         }
//         return false;
//     }
// };
// ```
// Next, we define `HolidayCalendar`:
// ```
// /// This class provides a value-semantic type that allows clients to
// /// modify and query a set of dates considered to be holidays.
// class HolidayCalendar {
// ```
// Here, we create a type alias, `DateSet`, for a `bsl::set` that will serve as
// the data member for a `HolidayCalendar`.  A `DateSet` has keys of type
// `MyDate`, and a comparator of type `MyDateLess`.  We use the default
// `ALLOCATOR` template parameter as we intend to use `HolidayCalendar` with
// `bslma` style allocators:
// ```
//     // PRIVATE TYPES
//
//     /// This `typedef` is an alias for a set of `MyDate` objects.
//     typedef bsl::set<MyDate, MyDateLess> DateSet;
//
//     // DATA
//     DateSet d_holidayDates;  // set of dates considered to be holidays
//
//   public:
//     // PUBLIC TYPES
//
//     /// This `typedef` provides an alias for the type of an iterator
//     /// providing non-modifiable access to holiday dates in a
//     /// `HolidayCalendar`.
//     typedef DateSet::const_iterator ConstIterator;
//
//     // CREATORS
//
//     /// Create an empty `HolidayCalendar` object.  Optionally specify a
//     /// `basicAllocator` used to supply memory.  If `basicAllocator` is
//     /// 0, the currently installed default allocator is used.
//     HolidayCalendar(bslma::Allocator *basicAllocator = 0);
//
//     /// Create a `HolidayCalendar` object having the same value as the
//     /// specified `original` object.  Optionally specify a
//     /// `basicAllocator` used to supply memory.  If `basicAllocator` is
//     /// 0, the currently installed default allocator is used.
//     HolidayCalendar(const HolidayCalendar&  original,
//                     bslma::Allocator       *basicAllocator = 0);
//
//     /// Destroy this object.
//     //! ~HolidayCalendar() = default;
//
//     // MANIPULATORS
//
//     /// Add the specified `date` as a holiday date maintained by this
//     /// calendar.  If `date` is already a holiday date, this method has
//     /// no effect.
//     void addHolidayDate(const MyDate& date);
//
//     /// Remove the specify `date` from the set of holiday dates
//     /// maintained by this calendar.  If `date` is not a holiday date,
//     /// this method has no effect.
//     void removeHolidayDate(const MyDate& date);
//
//     // ACCESSORS
//
//     /// Return `true` if the specified `date` is in the set of holiday
//     /// dates maintained by this calendar, and return `false` otherwise.
//     bool isHolidayDate(const MyDate& date) const;
//
//     /// Return an iterator providing non-modifiable access to the first
//     /// date in the ordered sequence of holiday dates maintained by this
//     /// calendar.
//     ConstIterator beginHolidayDates() const;
//
//     /// Return an iterator providing non-modifiable access to
//     /// past-the-end date in the ordered sequence of holiday dates
//     /// maintained by this calendar.
//     ConstIterator endHolidayDates() const;
// };
// ```
// Then, we declare the free operators for `HolidayCalendar`:
// ```
// /// Return `true` if the specified `lhs` and `rhs` objects have the same
// /// value, and `false` otherwise.  Two `HolidayCalendar` objects have
// /// the same value if they have the same number of holiday dates, and
// /// each corresponding holiday date, in their respective ordered
// /// sequence of dates, is the same.
// inline
// bool operator==(const HolidayCalendar& lhs, const HolidayCalendar& rhs);
//
// /// Return `true` if the specified `lhs` and `rhs` objects do not have
// /// the same value, and `false` otherwise.  Two `HolidayCalendar`
// /// objects do not have the same value if they either differ in their
// /// number of holiday dates, or if any of the corresponding holiday
// /// dates, in their respective ordered sequences of dates, is not the
// /// same.
// inline
// bool operator!=(const HolidayCalendar& lhs, const HolidayCalendar& rhs);
// ```
// Now, we define the implementations methods of the `HolidayCalendar` class:
// ```
// // CREATORS
// HolidayCalendar::HolidayCalendar(bslma::Allocator *basicAllocator)
// : d_holidayDates(basicAllocator)
// {
// }
// ```
// Notice that, on construction, we pass the `bsl::set` object the specified
// `bsl::Allocator` object.
// ```
// // MANIPULATORS
// void HolidayCalendar::addHolidayDate(const MyDate& date)
// {
//     d_holidayDates.insert(date);
// }
//
// void HolidayCalendar::removeHolidayDate(const MyDate& date)
// {
//     d_holidayDates.erase(date);
// }
//
// // ACCESSORS
// bool HolidayCalendar::isHolidayDate(const MyDate& date) const
// {
//     return d_holidayDates.find(date) != d_holidayDates.end();
// }
//
// HolidayCalendar::ConstIterator HolidayCalendar::beginHolidayDates() const
// {
//     return d_holidayDates.begin();
// }
//
// HolidayCalendar::ConstIterator HolidayCalendar::endHolidayDates() const
// {
//     return d_holidayDates.end();
// }
// ```
// Finally, we implement the free operators for `HolidayCalendar`:
// ```
// inline
// bool operator==(const HolidayCalendar& lhs, const HolidayCalendar& rhs)
// {
//     return lhs.d_holidayDates == rhs.d_holidayDates;
// }
//
// inline
// bool operator!=(const HolidayCalendar& lhs, const HolidayCalendar& rhs)
// {
//     return !(lhs == rhs);
// }
// ```

#include <bslscm_version.h>

#include <bslstl_algorithm.h>
#include <bslstl_iterator.h>
#include <bslstl_iteratorutil.h>
#include <bslstl_pair.h>
#include <bslstl_ranges.h>
#include <bslstl_setcomparator.h>
#include <bslstl_stdexceptutil.h>
#include <bslstl_treeiterator.h>
#include <bslstl_treenode.h>
#include <bslstl_treenodepool.h>

#include <bslalg_rangecompare.h>
#include <bslalg_rbtreeanchor.h>
#include <bslalg_rbtreenode.h>
#include <bslalg_rbtreeutil.h>
#include <bslalg_swaputil.h>
#include <bslalg_synththreewayutil.h>
#include <bslalg_typetraithasstliterators.h>

#include <bslma_isstdallocator.h>
#include <bslma_bslallocator.h>
#include <bslma_usesbslmaallocator.h>

#include <bslmf_containercompatiblerange.h>
#include <bslmf_isconvertible.h>
#include <bslmf_isnothrowswappable.h>
#include <bslmf_istransparentpredicate.h>
#include <bslmf_movableref.h>
#include <bslmf_typeidentity.h>
#include <bslmf_util.h>    // 'forward(V)'

#include <bsls_assert.h>
#include <bsls_compilerfeatures.h>
#include <bsls_keyword.h>
#include <bsls_libraryfeatures.h>
#include <bsls_performancehint.h>
#include <bsls_util.h>     // 'forward<T>(V)'

#include <functional>

#if defined(BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS)
# include <initializer_list>
#endif

#ifndef BDE_DONT_ALLOW_TRANSITIVE_INCLUDES
#include <bsls_nativestd.h>
#endif // BDE_DONT_ALLOW_TRANSITIVE_INCLUDES

#ifdef BSLS_COMPILERFEATURES_SUPPORT_TRAITS_HEADER
#include <type_traits>  // 'std::is_nothrow_move_assignable'
#endif

#if defined(BSLS_LIBRARYFEATURES_HAS_CPP20_CONCEPTS) \
 && defined(BSLS_LIBRARYFEATURES_HAS_CPP20_RANGES)
# define BSLSTL_SET_REQUIRES_CONTAINER_COMPATIBLE_RANGE(R, T) \
                  requires ::BloombergLP::bslmf::ContainerCompatibleRange<R, T>
#else
# define BSLSTL_SET_REQUIRES_CONTAINER_COMPATIBLE_RANGE(R, T)
#endif

#if BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES
// clang-format off
// Include version that can be compiled with C++03
// Generated on Mon Jan 13 08:31:39 2025
// Command line: sim_cpp11_features.pl bslstl_set.h

# define COMPILING_BSLSTL_SET_H
# include <bslstl_set_cpp03.h>
# undef COMPILING_BSLSTL_SET_H

// clang-format on
#else

namespace bsl {

                             // =========
                             // class set
                             // =========

/// This class template implements a value-semantic container type holding
/// an ordered sequence of unique keys (of the template parameter type,
/// `KEY`).
///
/// This class:
/// * supports a complete set of *value-semantic* operations
///   except for `BDEX` serialization
/// * is *exception-neutral* (agnostic except for the `at` method)
/// * is *alias-safe*
/// * is `const` *thread-safe*
/// For terminology see {`bsldoc_glossary`}.
template <class KEY,
          class COMPARATOR  = std::less<KEY>,
          class ALLOCATOR = allocator<KEY> >
class set {

    // PRIVATE TYPES

    /// This typedef is an alias for the type of key objects maintained by
    /// this set.
    typedef const KEY                                          ValueType;

    /// This typedef is an alias for the comparator used internally by this
    /// set.
    typedef BloombergLP::bslstl::SetComparator<KEY, COMPARATOR> Comparator;

    /// This typedef is an alias for the type of nodes held by the tree (of
    /// nodes) used to implement this set.
    typedef BloombergLP::bslstl::TreeNode<KEY>                 Node;

    /// This typedef is an alias for the factory type used to create and
    /// destroy `Node` objects.
    typedef BloombergLP::bslstl::TreeNodePool<KEY, ALLOCATOR>  NodeFactory;

    /// This typedef is an alias for the allocator traits type associated
    /// with this container.
    typedef bsl::allocator_traits<ALLOCATOR>                   AllocatorTraits;

    /// This typedef is a convenient alias for the utility associated with
    /// movable references.
    typedef BloombergLP::bslmf::MovableRefUtil                 MoveUtil;

    /// This class is a wrapper around the comparator and allocator data
    /// members.  It takes advantage of the empty-base optimization (EBO) so
    /// that if the comparator is stateless, it takes up no space.
    ///
    /// TBD: This struct should eventually be replaced by the use of a
    /// general EBO-enabled component that provides a `pair`-like interface
    /// or a `tuple`.
    class DataWrapper : public Comparator {

        // DATA
        NodeFactory d_pool;  // pool of 'Node' objects

      private:
        // NOT IMPLEMENTED
        DataWrapper(const DataWrapper&);
        DataWrapper& operator=(const DataWrapper&);

      public:
        // CREATORS

        /// Create a data wrapper using a copy of the specified `comparator`
        /// to order keys and a copy of the specified `basicAllocator` to
        /// supply memory.
        explicit DataWrapper(const COMPARATOR& comparator,
                             const ALLOCATOR&  basicAllocator);

        /// Create a data wrapper initialized to the contents of the `pool`
        /// associated with the specified `original` data wrapper.  The
        /// comparator and allocator associated with `original` are
        /// propagated to the new data wrapper.  `original` is left in a
        /// valid but unspecified state.
        DataWrapper(
              BloombergLP::bslmf::MovableRef<DataWrapper> original);// IMPLICIT

        // MANIPULATORS

        /// Return a reference providing modifiable access to the node
        /// factory associated with this data wrapper.
        NodeFactory& nodeFactory();

        // ACCESSORS

        /// Return a reference providing non-modifiable access to the node
        /// factory associated with this data wrapper.
        const NodeFactory& nodeFactory() const;
    };

    // DATA
    DataWrapper                       d_compAndAlloc;
                                               // comparator and pool of `Node`
                                               // objects

    BloombergLP::bslalg::RbTreeAnchor d_tree;  // balanced tree of `Node`
                                               // objects

  public:
    // PUBLIC TYPES
    typedef KEY                                        key_type;
    typedef KEY                                        value_type;
    typedef COMPARATOR                                 key_compare;
    typedef COMPARATOR                                 value_compare;
    typedef ALLOCATOR                                  allocator_type;
    typedef value_type&                                reference;
    typedef const value_type&                          const_reference;

    typedef typename AllocatorTraits::size_type        size_type;
    typedef typename AllocatorTraits::difference_type  difference_type;
    typedef typename AllocatorTraits::pointer          pointer;
    typedef typename AllocatorTraits::const_pointer    const_pointer;

    typedef BloombergLP::bslstl::TreeIterator<const value_type,
                                              Node,
                                              difference_type> iterator;
    typedef BloombergLP::bslstl::TreeIterator<const value_type,
                                              Node,
                                              difference_type> const_iterator;
    typedef bsl::reverse_iterator<iterator>            reverse_iterator;
    typedef bsl::reverse_iterator<const_iterator>      const_reverse_iterator;

  private:
    // PRIVATE MANIPULATORS

    /// Return a reference providing modifiable access to the node-allocator
    /// for this tree.
    NodeFactory& nodeFactory();

    /// Return a reference providing modifiable access to the comparator for
    /// this tree.
    Comparator& comparator();

    /// Efficiently exchange the value, comparator, and allocator of this
    /// object with the value, comparator, and allocator of the specified
    /// `other` object.  This method provides the no-throw exception-safety
    /// guarantee, *unless* swapping the (user-supplied) comparator or
    /// allocator objects can throw.
    void quickSwapExchangeAllocators(set& other);

    /// Efficiently exchange the value and comparator of this object with
    /// the value and comparator of the specified `other` object.  This
    /// method provides the no-throw exception-safety guarantee, *unless*
    /// swapping the (user-supplied) comparator objects can throw.  The
    /// behavior is undefined unless this object was created with the same
    /// allocator as `other`.
    void quickSwapRetainAllocators(set& other);

    /// Insert the values between the specified `first` and `last` into an
    /// initially empty set.  If sorted, directly place each value in its
    /// proper position. If an out of order value is detected, revert to
    /// normal insertion.
    template <class INPUT_ITERATOR, class SENTINEL>
    void constructFromRange(INPUT_ITERATOR first, SENTINEL last);

#if defined(BSLS_LIBRARYFEATURES_HAS_CPP20_CONCEPTS) \
 && defined(BSLS_LIBRARYFEATURES_HAS_CPP20_RANGES)

    /// Insert the values between the specified `first` and `last` into an
    /// initially empty set.  The specified 'numElements` is used to improve
    /// performance.  If sorted, directly place each value in its proper
    /// position. If an out of order value is detected, revert to
    /// normal insertion.  The behavior is undefined if the iterators support
    /// the calculation of distance and `numElements` is not the distance
    /// from `first` to `last`.
    template <class INPUT_ITERATOR, class SENTINEL>
    void constructFromRange(INPUT_ITERATOR first,
                            SENTINEL       last,
                            size_t         numElements);
#endif

    // Insert the values between `first` and `last` into this map.
    template <class INPUT_ITERATOR, class SENTINEL>
    void insertFromRange(INPUT_ITERATOR first,
                         SENTINEL       last);

#if defined(BSLS_LIBRARYFEATURES_HAS_CPP20_CONCEPTS) \
 && defined(BSLS_LIBRARYFEATURES_HAS_CPP20_RANGES)

    /// Insert the values between the specified `first` and `last` into this
    /// map. The specified `numElements` is used to improve performance.
    /// The behavior is undefined if the iterators support the calculation
    /// of distance and `numElements` is not the distance from `first` to
    /// `last`.
    template <class INPUT_ITERATOR, class SENTINEL>
    void insertFromRange(INPUT_ITERATOR first,
                         SENTINEL       last,
                         size_t         numElements);
#endif

    // PRIVATE ACCESSORS

    /// Return a reference providing non-modifiable access to the
    /// node-allocator for this tree.
    const NodeFactory& nodeFactory() const;

    /// Return a reference providing non-modifiable access to the comparator
    /// for this tree.
    const Comparator& comparator() const;

  public:
    // CREATORS

    /// Create an empty set.  Optionally specify a `comparator` used to
    /// order keys contained in this object.  If `comparator` is not
    /// supplied, a default-constructed object of the (template parameter)
    /// type `COMPARATOR` is used.  Optionally specify a `basicAllocator`
    /// used to supply memory.  If `basicAllocator` is not supplied, a
    /// default-constructed object of the (template parameter) type
    /// `ALLOCATOR` is used.  If the type `ALLOCATOR` is `bsl::allocator`
    /// and `basicAllocator` is not supplied, the currently installed
    /// default allocator is used.  Note that a `bslma::Allocator *` can be
    /// supplied for `basicAllocator` if the type `ALLOCATOR` is
    /// `bsl::allocator` (the default).
    set();
    explicit set(const COMPARATOR& comparator,
                 const ALLOCATOR&  basicAllocator = ALLOCATOR())
    : d_compAndAlloc(comparator, basicAllocator)
    , d_tree()
    {
        // The implementation is placed here in the class definition to work
        // around an AIX compiler bug, where the constructor can fail to
        // compile because it is unable to find the definition of the default
        // argument.  This occurs when a templatized class wraps around the
        // container and the comparator is defined after the new class.
    }

    /// Create an empty set that uses the specified `basicAllocator` to
    /// supply memory.  Use a default-constructed object of the (template
    /// parameter) type `COMPARATOR` to order the keys contained in this
    /// set.  Note that a `bslma::Allocator *` can be supplied for
    /// `basicAllocator` if the (template parameter) type `ALLOCATOR` is
    /// `bsl::allocator` (the default).
    explicit set(const ALLOCATOR& basicAllocator);

    /// Create a set having the same value as the specified `original`
    /// object.  Use a copy of `original.key_comp()` to order the keys
    /// contained in this set.  Use the allocator returned by
    /// `bsl::allocator_traits<ALLOCATOR>::
    /// select_on_container_copy_construction(original.get_allocator())` to
    /// allocate memory.  This method requires that the (template parameter)
    /// type `KEY` be `copy-insertable` into this set (see {Requirements on
    /// `KEY`}).
    set(const set& original);

    /// Create a set having the same value as the specified `original`
    /// object by moving (in constant time) the contents of `original` to
    /// the new set.  Use a copy of `original.key_comp()` to order the keys
    /// contained in this set.  The allocator associated with `original` is
    /// propagated for use in the newly-created set.  `original` is left in
    /// a valid but unspecified state.
    set(BloombergLP::bslmf::MovableRef<set> original);              // IMPLICIT

    /// Create a set having the same value as the specified `original`
    /// object that uses the specified `basicAllocator` to supply memory.
    /// Use a copy of `original.key_comp()` to order the keys contained in
    /// this set.  This method requires that the (template parameter) type
    /// `KEY` be `copy-insertable` into this set (see {Requirements on
    /// `KEY`}).  Note that a `bslma::Allocator *` can be supplied for
    /// `basicAllocator` if the (template parameter) type `ALLOCATOR` is
    /// `bsl::allocator` (the default).
    set(const set&                                     original,
        const typename type_identity<ALLOCATOR>::type& basicAllocator);

    /// Create a set having the same value as the specified `original`
    /// object that uses the specified `basicAllocator` to supply memory.
    /// The contents of `original` are moved (in constant time) to the new
    /// set if `basicAllocator == original.get_allocator()`, and are move-
    /// inserted (in linear time) using `basicAllocator` otherwise.
    /// `original` is left in a valid but unspecified state.  Use a copy of
    /// `original.key_comp()` to order the keys contained in this set.  This
    /// method requires that the (template parameter) type `KEY` be
    /// `move-insertable` into this set (see {Requirements on `KEY`}).  Note
    /// that a `bslma::Allocator *` can be supplied for `basicAllocator` if
    /// the (template parameter) type `ALLOCATOR` is `bsl::allocator` (the
    /// default).
    set(BloombergLP::bslmf::MovableRef<set>            original,
        const typename type_identity<ALLOCATOR>::type& basicAllocator);

    /// Create a set, and insert each `value_type` object in the sequence
    /// starting at the specified `first` element, and ending immediately
    /// before the specified `last` element, ignoring those keys having a
    /// value equivalent to that which appears earlier in the sequence.
    /// Optionally specify a `comparator` used to order keys contained in
    /// this object.  If `comparator` is not supplied, a default-constructed
    /// object of the (template parameter) type `COMPARATOR` is used.
    /// Optionally specify a `basicAllocator` used to supply memory.  If
    /// `basicAllocator` is not supplied, a default-constructed object of
    /// the (template parameter) type `ALLOCATOR` is used.  If the type
    /// `ALLOCATOR` is `bsl::allocator` and `basicAllocator` is not
    /// supplied, the currently installed default allocator is used.  If the
    /// sequence `first` to `last` is ordered according to `comparator`,
    /// then this operation has `O[N]` complexity, where `N` is the number
    /// of elements between `first` and `last`, otherwise this operation has
    /// `O[N * log(N)]` complexity.  The (template parameter) type
    /// `INPUT_ITERATOR` shall meet the requirements of an input iterator
    /// defined in the C++11 standard [24.2.3] providing access to values of
    /// a type convertible to `value_type`, and `value_type` must be
    /// `emplace-constructible` from `*i` into this set, where `i` is a
    /// dereferenceable iterator in the range `[first .. last)` (see
    /// {Requirements on `KEY`}).  The behavior is undefined unless `first`
    /// and `last` refer to a sequence of valid values where `first` is at a
    /// position at or before `last`.  Note that a `bslma::Allocator *` can
    /// be supplied for `basicAllocator` if the type `ALLOCATOR` is
    /// `bsl::allocator` (the default).
    template <class INPUT_ITERATOR>
    set(INPUT_ITERATOR    first,
        INPUT_ITERATOR    last,
        const COMPARATOR& comparator = COMPARATOR(),
        const ALLOCATOR&  basicAllocator = ALLOCATOR());
    template <class INPUT_ITERATOR>
    set(INPUT_ITERATOR    first,
        INPUT_ITERATOR    last,
        const ALLOCATOR&  basicAllocator);

    /// Create a set having the (`value_type`) values obtained from the
    /// specified `range`.  Ignore those those objects having a key equivalent
    /// to that which appears earlier in the sequence.  Optionally specify a
    /// `comparator` used to order key-value pairs contained in this object.
    /// If `comparator` is not supplied, a default-constructed object of the
    /// (template parameter) type `COMPARATOR` is used.  Optionally specify a
    /// `basicAllocator` used to supply memory.  If `basicAllocator` is not
    /// supplied, a default-constructed object of the (template parameter) type
    /// `ALLOCATOR` is used.  If the type `ALLOCATOR` is `bsl::allocator`
    /// (the default), then `basicAllocator`, if supplied, shall be
    /// convertible to `bslma::Allocator *`.  If the type `ALLOCATOR` is
    /// `bsl::allocator` and `basicAllocator` is not supplied, the currently
    /// installed default allocator is used.  If values obtained from `range
    /// are ordered according to `comparator`, then this operation has `O[N]`
    /// complexity, where `N` is the number of values in the `range`;
    /// otherwise, this operation has `O[N * log(N)]` complexity.  Note that
    /// `RANGE` must meet the requirements of an input range and the values
    /// from `range` must have a type matching or convertible to `value_type`.
    template <class RANGE>
    BSLSTL_SET_REQUIRES_CONTAINER_COMPATIBLE_RANGE(RANGE, value_type)
    set(bsl::from_range_t                        ,
        BSLS_COMPILERFEATURES_FORWARD_REF(RANGE) range,
        const COMPARATOR&                        comparator     = COMPARATOR(),
        const ALLOCATOR&                         basicAllocator = ALLOCATOR())
    : d_compAndAlloc(comparator, basicAllocator)
    , d_tree()
    {
        // Defined inline to avoid Windows errors.

#if defined(BSLS_LIBRARYFEATURES_HAS_CPP20_CONCEPTS) \
 && defined(BSLS_LIBRARYFEATURES_HAS_CPP20_RANGES)
        if constexpr (ranges::sized_range<RANGE>) {
            constructFromRange(bsl::ranges::begin(range),
                               bsl::ranges::end  (range),
                               bsl::ranges::size (range));
        } else // ...
#endif
        {
            constructFromRange(bsl::ranges::begin(range),
                               bsl::ranges::end  (range));
        }
    }

    template <class RANGE>
    BSLSTL_SET_REQUIRES_CONTAINER_COMPATIBLE_RANGE(RANGE, value_type)
    set(from_range_t                             ,
        BSLS_COMPILERFEATURES_FORWARD_REF(RANGE) range,
        const ALLOCATOR&                         basicAllocator)
    : d_compAndAlloc(COMPARATOR(), basicAllocator)
    , d_tree()
    {
        // Defined inline to avoid Windows errors.

        set other(bsl::from_range,
                  range,
                  COMPARATOR(),
                  nodeFactory().allocator());
        quickSwapRetainAllocators(other);
    }

#if defined(BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS)
    /// Create a set and insert each `value_type` object in the specified
    /// `values` initializer list, ignoring those keys having a value
    /// equivalent to that which appears earlier in the list.  Optionally
    /// specify a `comparator` used to order keys contained in this object.
    /// If `comparator` is not supplied, a default-constructed object of the
    /// (template parameter) type `COMPARATOR` is used.  Optionally specify
    /// a `basicAllocator` used to supply memory.  If `basicAllocator` is
    /// not supplied, a default-constructed object of the (template
    /// parameter) type `ALLOCATOR` is used.  If the type `ALLOCATOR` is
    /// `bsl::allocator` and `basicAllocator` is not supplied, the currently
    /// installed default allocator is used.  If `values` is ordered
    /// according to `comparator`, then this operation has `O[N]`
    /// complexity, where `N` is the number of elements in `list`; otherwise
    /// this operation has `O[N * log(N)]` complexity.  This method requires
    /// that the (template parameter) type `KEY` be `copy-insertable` into
    /// this set (see {Requirements on `KEY`}).  Note that a
    /// `bslma::Allocator *` can be supplied for `basicAllocator` if the
    /// type `ALLOCATOR` is `bsl::allocator` (the default).
    set(std::initializer_list<KEY> values,
        const COMPARATOR&          comparator = COMPARATOR(),
        const ALLOCATOR&           basicAllocator = ALLOCATOR());
    set(std::initializer_list<KEY> values,
        const ALLOCATOR&           basicAllocator);
#endif

    /// Destroy this object.
    ~set();

    // MANIPULATORS

    /// Assign to this object the value and comparator of the specified
    /// `rhs` object, propagate to this object the allocator of `rhs` if the
    /// `ALLOCATOR` type has trait `propagate_on_container_copy_assignment`,
    /// and return a reference providing modifiable access to this object.
    /// If an exception is thrown, `*this` is left in a valid but
    /// unspecified state.  This method requires that the (template
    /// parameter) type `KEY` be `copy-assignable` and `copy-insertable`
    /// into this set (see {Requirements on `KEY`}).
    set& operator=(const set& rhs);

    /// Assign to this object the value and comparator of the specified
    /// `rhs` object, propagate to this object the allocator of `rhs` if the
    /// `ALLOCATOR` type has trait `propagate_on_container_move_assignment`,
    /// and return a reference providing modifiable access to this object.
    /// The contents of `rhs` are moved (in constant time) to this set if
    /// `get_allocator() == rhs.get_allocator()` (after accounting for the
    /// aforementioned trait); otherwise, all elements in this set are
    /// either destroyed or move-assigned to and each additional element in
    /// `rhs` is move-inserted into this set.  `rhs` is left in a valid but
    /// unspecified state, and if an exception is thrown, `*this` is left
    /// in a valid but unspecified state.  This method requires that the
    /// (template parameter) type `KEY` be `move-assignable` and
    /// `move-insertable` into this set (see {Requirements on `KEY`}).
    set& operator=(BloombergLP::bslmf::MovableRef<set> rhs)
                       BSLS_KEYWORD_NOEXCEPT_SPECIFICATION(
                           AllocatorTraits::is_always_equal::value
                        && std::is_nothrow_move_assignable<COMPARATOR>::value);

#if defined(BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS)
    /// Assign to this object the value resulting from first clearing this
    /// set and then inserting each `value_type` object in the specified
    /// `values` initializer list, ignoring those keys having a value
    /// equivalent to that which appears earlier in the list; return a
    /// reference providing modifiable access to this object.  This method
    /// requires that the (template parameter) type `KEY` be
    /// `copy-insertable` into this set (see {Requirements on `KEY`}).
    set& operator=(std::initializer_list<KEY> values);
#endif

    /// Return an iterator providing modifiable access to the first
    /// `value_type` object in the ordered sequence of `value_type` objects
    /// maintained by this set, or the `end` iterator if this set is empty.
    iterator begin() BSLS_KEYWORD_NOEXCEPT;

    /// Return an iterator providing modifiable access to the past-the-end
    /// element in the ordered sequence of `value_type` objects maintained
    /// by this set.
    iterator end() BSLS_KEYWORD_NOEXCEPT;

    /// Return a reverse iterator providing modifiable access to the last
    /// `value_type` object in the ordered sequence of `value_type` objects
    /// maintained by this set, or `rend` if this object is empty.
    reverse_iterator rbegin() BSLS_KEYWORD_NOEXCEPT;

    /// Return a reverse iterator providing modifiable access to the
    /// prior-to-the-beginning element in the ordered sequence of
    /// `value_type` objects maintained by this set.
    reverse_iterator rend() BSLS_KEYWORD_NOEXCEPT;

    /// Insert the specified `value` into this set if a key equivalent to
    /// `value` does not already exist in this set; otherwise, if a key
    /// equivalent to `value` already exists in this set, this method has no
    /// effect.  Return a pair whose `first` member is an iterator referring
    /// to the (possibly newly inserted) `value_type` object in this set
    /// that is equivalent to `value`, and whose `second` member is `true`
    /// if a new value was inserted, and `false` if the key was already
    /// present.  This method requires that the (template parameter) type
    /// `KEY` be `copy-insertable` into this set (see {Requirements on
    /// `KEY`}).
    pair<iterator, bool> insert(const value_type& value);

    /// Insert the specified `value` into this set if a key equivalent to
    /// `value` does not already exist in this set; otherwise, if a key
    /// equivalent to `value` already exists in this set, this method has no
    /// effect.  `value` is left in a valid but unspecified state.  Return a
    /// pair whose `first` member is an iterator referring to the (possibly
    /// newly inserted) `value_type` object in this set that is equivalent
    /// to `value`, and whose `second` member is `true` if a new value was
    /// inserted, and `false` if the key was already present.  This method
    /// requires that the (template parameter) type `KEY` be
    /// `move-insertable` (see {Requirements on `KEY`}).
    pair<iterator, bool> insert(
                             BloombergLP::bslmf::MovableRef<value_type> value);

#if !BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES
    /// Insert the specified `value` into this set if a key equivalent to
    /// `value` does not already exist in this set; otherwise, if a key
    /// equivalent to `value` already exists in this set, this method has no
    /// effect.  `value` is left in a valid but unspecified state.  Return a
    /// pair whose `first` member is an iterator referring to the (possibly
    /// newly inserted) `value_type` object in this set that is equivalent
    /// to `value`, and whose `second` member is `true` if a new value was
    /// inserted, and `false` if the key was already present.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    template <class LOOKUP_KEY>
    typename enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   LOOKUP_KEY>::value
        , pair<iterator, bool> >::type
    insert(LOOKUP_KEY&& value)
    {
        typedef pair<iterator, bool> Result;

        int comparisonResult;
        BloombergLP::bslalg::RbTreeNode *insertLocation =
            BloombergLP::bslalg::RbTreeUtil::findUniqueInsertLocation(
                                                            &comparisonResult,
                                                            &d_tree,
                                                            this->comparator(),
                                                            value);
        if (!comparisonResult) {
            return Result(iterator(insertLocation), false);           // RETURN
        }
        BloombergLP::bslalg::RbTreeNode *node =
            nodeFactory().emplaceIntoNewNode(
                             BSLS_COMPILERFEATURES_FORWARD(LOOKUP_KEY, value));
        BloombergLP::bslalg::RbTreeUtil::insertAt(&d_tree,
                                                  insertLocation,
                                                  comparisonResult < 0,
                                                  node);
        return Result(iterator(node), true);
    }
#endif

    /// Insert the specified `value` into this set (in amortized constant
    /// time if the specified `hint` is a valid immediate successor to
    /// `value`), if a key equivalent to `value` does not already exist in
    /// this set; otherwise, if a key equivalent to `value` already exists
    /// in this set, this method has no effect.  Return an iterator
    /// referring to the (possibly newly inserted) `value_type` object in
    /// this set that is equivalent to `value`.  If `hint` is not a valid
    /// immediate successor to `value`, this operation has `O[log(N)]`
    /// complexity, where `N` is the size of this set.  This method requires
    /// that the (template parameter) type `KEY` be `copy-insertable` into
    /// this set (see {Requirements on `KEY`}).  The behavior is undefined
    /// unless `hint` is an iterator in the range `[begin() .. end()]` (both
    /// endpoints included).
    iterator insert(const_iterator hint, const value_type& value);

    /// Insert the specified `value` into this set (in amortized constant
    /// time if the specified `hint` is a valid immediate successor to
    /// `value`) if a key equivalent to `value` does not already exist in
    /// this set; otherwise, this method has no effect.  `value` is left in
    /// a valid but unspecified state.  Return an iterator referring to the
    /// (possibly newly inserted) `value_type` object in this set that is
    /// equivalent to `value`.  If `hint` is not a valid immediate successor
    /// to `value`, this operation has `O[log(N)]` complexity, where `N` is
    /// the size of this set.  This method requires that the (template
    /// parameter) type `KEY` be `move-insertable` (see {Requirements on
    /// `KEY`}).  The behavior is undefined unless `hint` is an iterator in
    /// the range `[begin() .. end()]` (both endpoints included).
    iterator insert(const_iterator                             hint,
                    BloombergLP::bslmf::MovableRef<value_type> value);

#if !BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES
    /// Insert the specified `value` into this set if a key equivalent to
    /// `value` does not already exist in this set; otherwise, if a key
    /// equivalent to `value` already exists in this set, this method has no
    /// effect.  `value` is left in a valid but unspecified state.  Return
    /// an iterator referring to the (possibly newly inserted) `value_type`
    /// object in this set that is equivalent to `value`.  The average and
    /// worst case complexity of this operation is not affected by the
    /// specified `hint`.  This method requires that the (template
    /// parameter) type `KEY` be `move-insertable` (see {Requirements on
    /// `KEY`}) into this set.  The behavior is undefined unless `hint` is
    /// an iterator in the range `[begin() .. end()]` (both endpoints
    /// included).  Note that `hint` is ignored (other than possibly
    /// asserting its validity in some build modes).
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    template <class LOOKUP_KEY>
    typename enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   LOOKUP_KEY>::value
        && !bsl::is_convertible<LOOKUP_KEY&&, iterator>::value
        && !bsl::is_convertible<LOOKUP_KEY&&, const_iterator>::value
         , iterator>::type
    insert(const_iterator hint, LOOKUP_KEY&& value)
    {
        BloombergLP::bslalg::RbTreeNode *hintNode =
                    const_cast<BloombergLP::bslalg::RbTreeNode *>(hint.node());

        int comparisonResult;
        BloombergLP::bslalg::RbTreeNode *insertLocation =
            BloombergLP::bslalg::RbTreeUtil::findUniqueInsertLocation(
                                                            &comparisonResult,
                                                            &d_tree,
                                                            this->comparator(),
                                                            value,
                                                            hintNode);
        if (!comparisonResult) {
            return iterator(insertLocation);                          // RETURN
        }

        BloombergLP::bslalg::RbTreeNode *node =
            nodeFactory().emplaceIntoNewNode(
                             BSLS_COMPILERFEATURES_FORWARD(LOOKUP_KEY, value));

        BloombergLP::bslalg::RbTreeUtil::insertAt(&d_tree,
                                                  insertLocation,
                                                  comparisonResult < 0,
                                                  node);
        return iterator(node);
    }
#endif

    /// Insert into this set the value of each `value_type` object in the
    /// range starting at the specified `first` iterator and ending
    /// immediately before the specified `last` iterator, if a key
    /// equivalent to the object is not already contained in this set.  The
    /// (template parameter) type `INPUT_ITERATOR` shall meet the
    /// requirements of an input iterator defined in the C++11 standard
    /// [24.2.3] providing access to values of a type convertible to
    /// `value_type`, and `value_type` must be `emplace-constructible` from
    /// `*i` into this set, where `i` is a dereferenceable iterator in the
    /// range `[first .. last)` (see {Requirements on `KEY`}).  The behavior
    /// is undefined unless `first` and `last` refer to a sequence of valid
    /// values where `first` is at a position at or before `last`.
    template <class INPUT_ITERATOR>
    void insert(INPUT_ITERATOR first, INPUT_ITERATOR last);

#if defined(BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS)
    /// Insert into this set the value of each `value_type` object in the
    /// specified `values` initializer list if a key equivalent to the
    /// object is not already contained in this set.  This method requires
    /// that the (template parameter) type `KEY` be `copy-insertable` (see
    /// {Requirements on `KEY`}).
    void insert(std::initializer_list<KEY> values);
#endif

    /// Insert into this set the value of each `value_type` object in the
    /// specified `range` if the key equivalent of that object is not
    /// already contained in this map.  The (template parameter) type `RANGE`
    /// must meet the requirements the C++20 standard [ranges] providing access
    /// to values of a type convertible to `value_type`, and `value_type` must
    /// be `emplace-constructible` from `*i` into this map, where `i` is a
    /// dereferenceable iterator obtained from `range` (see {Requirements on
    /// `KEY`}).  The behavior is undefined if `range` overlaps this set.
    template <class RANGE>
    BSLSTL_SET_REQUIRES_CONTAINER_COMPATIBLE_RANGE(RANGE, value_type)
    void insert_range(BSLS_COMPILERFEATURES_FORWARD_REF(RANGE) range)
    {
        // Defined inline to avoid Windows errors.

#if defined(BSLS_LIBRARYFEATURES_HAS_CPP20_CONCEPTS) \
 && defined(BSLS_LIBRARYFEATURES_HAS_CPP20_RANGES)
        if constexpr (ranges::sized_range<RANGE>) {
            insertFromRange(bsl::ranges::begin(range),
                            bsl::ranges::end  (range),
                            bsl::ranges::size (range));
        } else // ...
#endif
        {
            insertFromRange(bsl::ranges::begin(range),
                            bsl::ranges::end  (range));
        }
    }

#if !BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES

    /// Insert into this set a newly created `value_type` object,
    /// constructed by forwarding `get_allocator()` (if required) and the
    /// specified (variable number of) `arguments` to the corresponding
    /// constructor of `value_type`, if a key equivalent to such a value
    /// does not already exist in this set; otherwise, this method has no
    /// effect (other than possibly creating a temporary `value_type`
    /// object).  Return a pair whose `first` member is an iterator
    /// referring to the (possibly newly created and inserted) object in
    /// this set whose value is equivalent to that of an object constructed
    /// from `arguments`, and whose `second` member is `true` if a new value
    /// was inserted, and `false` if an equivalent key was already present.
    /// This method requires that the (template parameter) type `KEY` be
    /// `emplace-constructible` from `arguments` (see {Requirements on
    /// `KEY`}).
    template <class... Args>
    pair<iterator, bool> emplace(Args&&... arguments);

    /// Insert into this set a newly created `value_type` object,
    /// constructed by forwarding `get_allocator()` (if required) and the
    /// specified (variable number of) `arguments` to the corresponding
    /// constructor of `value_type`, (in amortized constant time if the
    /// specified `hint` is a valid immediate successor to the `value_type`
    /// object constructed from `arguments`), if a key equivalent to such a
    /// value does not already exist in this set; otherwise, this method has
    /// no effect (other than possibly creating a temporary `value_type`
    /// object).  Return an iterator referring to the (possibly newly
    /// created and inserted) object in this set whose value is equivalent
    /// to that of an object constructed from `arguments`.  If `hint` is not
    /// a valid immediate successor to the `value_type` object implied by
    /// `arguments`, this operation has `O[log(N)]` complexity where `N` is
    /// the size of this set.  This method requires that the (template
    /// parameter) type `KEY` be `emplace-constructible` from `arguments`
    /// (see {Requirements on `KEY`}).  The behavior is undefined unless
    /// `hint` is an iterator in the range `[begin() .. end()]` (both
    /// endpoints included).
    template <class... Args>
    iterator emplace_hint(const_iterator hint, Args&&... arguments);

#endif

    /// Remove from this set the `value_type` object at the specified
    /// `position`, and return an iterator referring to the element
    /// immediately following the removed element, or to the past-the-end
    /// position if the removed element was the last element in the sequence
    /// of elements maintained by this set.   This method invalidates only
    /// iterators and references to the removed element and previously saved
    /// values of the `end()` iterator.  The behavior is undefined unless
    /// `position` refers to a `value_type` object in this set.
    iterator erase(const_iterator position);

    /// Remove from this set the `value_type` object that is equivalent to
    /// the specified `key`, if such an entry exists, and return 1;
    /// otherwise, if there is no `value_type` object that is equivalent to
    /// `key`, return 0 with no other effect.   This method invalidates only
    /// iterators and references to the removed element and previously saved
    /// values of the `end()` iterator.
    size_type erase(const key_type& key);
    template <class t_KEY>
    typename enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   t_KEY>::value &&
        !is_convertible<BSLS_COMPILERFEATURES_FORWARD_REF(t_KEY),
                        iterator>::value &&
        !is_convertible<BSLS_COMPILERFEATURES_FORWARD_REF(t_KEY),
                        const_iterator>::value,
    size_type>::type erase(BSLS_COMPILERFEATURES_FORWARD_REF(t_KEY) key)
    {
        // Implemented inline due to Sun CC compilation error.
        iterator it = this->find(key);
        if (it == end()) {
            return 0;                                                 // RETURN
        }
        erase(it);
        return 1;
    }

    /// Remove from this set the `value_type` objects starting at the
    /// specified `first` position up to, but including the specified `last`
    /// position, and return `last`.   This method invalidates only
    /// iterators and references to the removed element and previously saved
    /// values of the `end()` iterator.  The behavior is undefined unless
    /// `first` and `last` either refer to elements in this set or are the
    /// `end` iterator, and the `first` position is at or before the `last`
    /// position in the ordered sequence provided by this container.
    iterator erase(const_iterator first, const_iterator last);

    /// Exchange the value and comparator of this object with those of the
    /// specified `other` object; also exchange the allocator of this object
    /// with that of `other` if the (template parameter) type `ALLOCATOR`
    /// has the `propagate_on_container_swap` trait, and do not modify
    /// either allocator otherwise.  This method provides the no-throw
    /// exception-safety guarantee if and only if the (template parameter)
    /// type `COMPARATOR` provides a no-throw swap operation, and provides
    /// the basic exception-safety guarantee otherwise; if an exception is
    /// thrown, both objects are left in valid but unspecified states.  This
    /// operation has `O[1]` complexity if either this object was created
    /// with the same allocator as `other` or `ALLOCATOR` has the
    /// `propagate_on_container_swap` trait; otherwise, it has `O[n + m]`
    /// complexity, where `n` and `m` are the number of elements in this
    /// object and `other`, respectively.  Note that this method`s support
    /// for swapping objects created with different allocators when
    /// `ALLOCATOR` does not have the `propagate_on_container_swap` trait is
    /// a departure from the C++ Standard.
    void swap(set& other) BSLS_KEYWORD_NOEXCEPT_SPECIFICATION(
                                 AllocatorTraits::is_always_equal::value
                              && bsl::is_nothrow_swappable<COMPARATOR>::value);

    /// Remove all entries from this set.  Note that the set is empty after
    /// this call, but allocated memory may be retained for future use.
    void clear() BSLS_KEYWORD_NOEXCEPT;

    // Turn off complaints about necessarily class-defined methods.
    // BDE_VERIFY pragma: push
    // BDE_VERIFY pragma: -CD01

    /// Return an iterator providing modifiable access to the `value_type`
    /// object in this set that is equivalent to the specified `key`, if
    /// such an entry exists, and the past-the-end (`end`) iterator
    /// otherwise.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    iterator find(const key_type& key)
    {
        return iterator(BloombergLP::bslalg::RbTreeUtil::find(
            d_tree, this->comparator(), key));
    }

    /// Return an iterator providing modifiable access to the `value_type`
    /// object in this set that is equivalent to the specified `key`, if
    /// such an entry exists, and the past-the-end (`end`) iterator
    /// otherwise.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    template <class LOOKUP_KEY>
    typename bsl::enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   LOOKUP_KEY>::value,
        iterator>::type
    find(const LOOKUP_KEY& key)
    {
        return iterator(BloombergLP::bslalg::RbTreeUtil::find(
            d_tree, this->comparator(), key));
    }

    /// Return an iterator providing modifiable access to the first (i.e.,
    /// ordered least) `value_type` object in this set greater-than or
    /// equal-to the specified `key`, and the past-the-end iterator if this
    /// set does not contain a `value_type` object greater-than or equal-to
    /// `key`.  Note that this function returns the *first* position before
    /// which a `value_type` object equivalent to `key` could be inserted
    /// into the ordered sequence maintained by this set, while preserving
    /// its ordering.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    iterator lower_bound(const key_type& key)
    {
        return iterator(BloombergLP::bslalg::RbTreeUtil::lowerBound(
            d_tree, this->comparator(), key));
    }

    /// Return an iterator providing modifiable access to the first (i.e.,
    /// ordered least) `value_type` object in this set greater-than or
    /// equal-to the specified `key`, and the past-the-end iterator if this
    /// set does not contain a `value_type` object greater-than or equal-to
    /// `key`.  Note that this function returns the *first* position before
    /// which a `value_type` object equivalent to `key` could be inserted
    /// into the ordered sequence maintained by this set, while preserving
    /// its ordering.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    template <class LOOKUP_KEY>
    typename bsl::enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   LOOKUP_KEY>::value,
        iterator>::type
    lower_bound(const LOOKUP_KEY& key)
    {
        return iterator(BloombergLP::bslalg::RbTreeUtil::lowerBound(
            d_tree, this->comparator(), key));
    }

    /// Return an iterator providing modifiable access to the first (i.e.,
    /// ordered least) `value_type` object in this set greater than the
    /// specified `key`, and the past-the-end iterator if this set does not
    /// contain a `value_type` object greater-than `key`.  Note that this
    /// function returns the *last* position before which a `value_type`
    /// object equivalent to `key` could be inserted into the ordered
    /// sequence maintained by this set, while preserving its ordering.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    iterator upper_bound(const key_type& key)
    {
        return iterator(BloombergLP::bslalg::RbTreeUtil::upperBound(
            d_tree, this->comparator(), key));
    }

    /// Return an iterator providing modifiable access to the first (i.e.,
    /// ordered least) `value_type` object in this set greater than the
    /// specified `key`, and the past-the-end iterator if this set does not
    /// contain a `value_type` object greater-than `key`.  Note that this
    /// function returns the *last* position before which a `value_type`
    /// object equivalent to `key` could be inserted into the ordered
    /// sequence maintained by this set, while preserving its ordering.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    template <class LOOKUP_KEY>
    typename bsl::enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   LOOKUP_KEY>::value,
        iterator>::type
    upper_bound(const LOOKUP_KEY& key)
    {
        return iterator(BloombergLP::bslalg::RbTreeUtil::upperBound(
            d_tree, this->comparator(), key));
    }

    /// Return a pair of iterators providing modifiable access to the
    /// sequence of `value_type` objects in this set that are equivalent to
    /// the specified `key`, where the first iterator is positioned at the
    /// start of the sequence, and the second is positioned one past the end
    /// of the sequence.  The first returned iterator will be
    /// `lower_bound(key)`; the second returned iterator will be
    /// `upper_bound(key)`; and, if this set contains no `value_type`
    /// objects equivalent to `key`, then the two returned iterators will
    /// have the same value.  Note that since a set maintains unique keys,
    /// the range will contain at most one element.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    pair<iterator, iterator> equal_range(const key_type& key)
    {
        iterator startIt = lower_bound(key);
        iterator endIt   = startIt;
        if (endIt != end() && !comparator()(key, *endIt.node())) {
            ++endIt;
        }
        return pair<iterator, iterator>(startIt, endIt);
    }

    /// Return a pair of iterators providing modifiable access to the
    /// sequence of `value_type` objects in this set that are equivalent to
    /// the specified `key`, where the first iterator is positioned at the
    /// start of the sequence, and the second is positioned one past the end
    /// of the sequence.  The first returned iterator will be
    /// `lower_bound(key)`; the second returned iterator will be
    /// `upper_bound(key)`; and, if this set contains no `value_type`
    /// objects equivalent to `key`, then the two returned iterators will
    /// have the same value.  Note that although a set maintains unique
    /// keys, the range may contain more than one element, because a
    /// transparent comparator may have been supplied that provides a
    /// different (but compatible) partitioning of keys for `LOOKUP_KEY` as
    /// the comparisons used to order the keys in the set.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    template <class LOOKUP_KEY>
    typename bsl::enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   LOOKUP_KEY>::value,
        pair<iterator, iterator> >::type
    equal_range(const LOOKUP_KEY& key)
    {
        iterator startIt = lower_bound(key);
        iterator endIt   = startIt;
        if (endIt != end() && !comparator()(key, *endIt.node())) {
            ++endIt;

            // Typically, even with a transparent comparator, we expect to find
            // either 0 or 1 matching keys. We test for those two common cases
            // before performing a logarithmic search via 'upper_bound' to
            // determine the end of the range.

            if (endIt != end() && !comparator()(key, *endIt.node())) {
                endIt = upper_bound(key);
            }
        }
        return pair<iterator, iterator>(startIt, endIt);
    }

    // BDE_VERIFY pragma: pop

    // ACCESSORS

    /// Return (a copy of) the allocator used for memory allocation by this
    /// set.
    allocator_type get_allocator() const BSLS_KEYWORD_NOEXCEPT;

    /// Return an iterator providing non-modifiable access to the first
    /// `value_type` object in the ordered sequence of `value_type` objects
    /// maintained by this set, or the `end` iterator if this set is empty.
    const_iterator begin() const BSLS_KEYWORD_NOEXCEPT;

    /// Return an iterator providing non-modifiable access to the
    /// past-the-end element in the ordered sequence of `value_type`
    /// objects maintained by this set.
    const_iterator end() const BSLS_KEYWORD_NOEXCEPT;

    /// Return a reverse iterator providing non-modifiable access to the
    /// last `value_type` object in the ordered sequence of `value_type`
    /// objects maintained by this set, or `rend` if this object is empty.
    const_reverse_iterator rbegin() const BSLS_KEYWORD_NOEXCEPT;

    /// Return a reverse iterator providing non-modifiable access to the
    /// prior-to-the-beginning element in the ordered sequence of
    /// `value_type` objects maintained by this set.
    const_reverse_iterator rend() const BSLS_KEYWORD_NOEXCEPT;

    /// Return an iterator providing non-modifiable access to the first
    /// `value_type` object in the ordered sequence of `value_type` objects
    /// maintained by this set, or the `cend` iterator if this set is empty.
    const_iterator cbegin() const BSLS_KEYWORD_NOEXCEPT;

    /// Return an iterator providing non-modifiable access to the
    /// past-the-end element in the ordered sequence of `value_type` objects
    /// maintained by this set.
    const_iterator cend() const BSLS_KEYWORD_NOEXCEPT;

    /// Return a reverse iterator providing non-modifiable access to the
    /// last `value_type` object in the ordered sequence of `value_type`
    /// objects maintained by this set, or `crend` if this set is empty.
    const_reverse_iterator crbegin() const BSLS_KEYWORD_NOEXCEPT;

    /// Return a reverse iterator providing non-modifiable access to the
    /// prior-to-the-beginning element in the ordered sequence of
    /// `value_type` objects maintained by this set.
    const_reverse_iterator crend() const BSLS_KEYWORD_NOEXCEPT;

    /// Return `true` if this map contains an element whose key is
    /// equivalent to the specified `key`.
    bool contains(const key_type &key) const;

    /// Return `true` if this map contains an element whose key is
    /// equivalent to the specified `key`.
    ///
    /// Note: implemented inline due to Sun CC compilation error
    template <class LOOKUP_KEY>
    typename bsl::enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   LOOKUP_KEY>::value,
        bool>::type
    contains(const LOOKUP_KEY& key) const
    {
        return find(key) != end();
    }

    /// Return `true` if this set contains no elements, and `false`
    /// otherwise.
    bool empty() const BSLS_KEYWORD_NOEXCEPT;

    /// Return the number of elements in this set.
    size_type size() const BSLS_KEYWORD_NOEXCEPT;

    /// Return a theoretical upper bound on the largest number of elements
    /// that this set could possibly hold.  Note that there is no guarantee
    /// that the set can successfully grow to the returned size, or even
    /// close to that size without running out of resources.
    size_type max_size() const BSLS_KEYWORD_NOEXCEPT;

    /// Return the key-comparison functor (or function pointer) used by this
    /// set; if a comparator was supplied at construction, return its value,
    /// otherwise return a default constructed `key_compare` object.  Note
    /// that this comparator compares objects of type `KEY`, which is the
    /// type of the `value_type` objects contained in this set.
    key_compare key_comp() const;

    /// Return a functor for comparing two `value_type` objects using
    /// `key_comp()`.  Note that since `value_type` is an alias to `KEY` for
    /// `set`, this method returns the same functor as `key_comp()`.
    value_compare value_comp() const;

    // Turn off complaints about necessarily class-defined methods.
    // BDE_VERIFY pragma: push
    // BDE_VERIFY pragma: -CD01

    /// Return an iterator providing non-modifiable access to the
    /// `value_type` object in this set that is equivalent to the specified
    /// `key`, if such an entry exists, and the past-the-end (`end`)
    /// iterator otherwise.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    const_iterator find(const key_type& key) const
    {
        return const_iterator(BloombergLP::bslalg::RbTreeUtil::find(
            d_tree, this->comparator(), key));
    }

    /// Return an iterator providing non-modifiable access to the
    /// `value_type` object in this set that is equivalent to the specified
    /// `key`, if such an entry exists, and the past-the-end (`end`)
    /// iterator otherwise.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    template <class LOOKUP_KEY>
    typename bsl::enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   LOOKUP_KEY>::value,
        const_iterator>::type
    find(const LOOKUP_KEY& key) const
    {
        return const_iterator(BloombergLP::bslalg::RbTreeUtil::find(
            d_tree, this->comparator(), key));
    }

    /// Return the number of `value_type` objects within this set that are
    /// equivalent to the specified `key`.  Note that since a set maintains
    /// unique keys, the returned value will be either 0 or 1.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    size_type count(const key_type& key) const
    {
        return (find(key) != end()) ? 1 : 0;
    }

    /// Return the number of `value_type` objects within this set that are
    /// equivalent to the specified `key`.  Note that although a set
    /// maintains unique keys, the returned value can be other than 0 or 1,
    /// because a transparent comparator may have been supplied that
    /// provides a different (but compatible) partitioning of keys for
    /// `LOOKUP_KEY` as the comparisons used to order the keys in the set.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    template <class LOOKUP_KEY>
    typename bsl::enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   LOOKUP_KEY>::value,
        size_type>::type
    count(const LOOKUP_KEY& key) const
    {
        int            count = 0;
        const_iterator it    = lower_bound(key);

        while (it != end() && !comparator()(key, *it.node())) {
            ++it;
            ++count;
        }
        return count;
    }

    /// Return an iterator providing non-modifiable access to the first
    /// (i.e., ordered least) `value_type` object in this set greater-than
    /// or equal-to the specified `key`, and the past-the-end iterator if
    /// this set does not contain a `value_type` greater-than or equal-to
    /// `key`.  Note that this function returns the *first* position before
    /// which a `value_type` object equivalent to `key` could be inserted
    /// into the ordered sequence maintained by this set, while preserving
    /// its ordering.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    const_iterator lower_bound(const key_type& key) const
    {
        return const_iterator(BloombergLP::bslalg::RbTreeUtil::lowerBound(
            d_tree, this->comparator(), key));
    }

    /// Return an iterator providing non-modifiable access to the first
    /// (i.e., ordered least) `value_type` object in this set greater-than
    /// or equal-to the specified `key`, and the past-the-end iterator if
    /// this set does not contain a `value_type` greater-than or equal-to
    /// `key`.  Note that this function returns the *first* position before
    /// which a `value_type` object equivalent to `key` could be inserted
    /// into the ordered sequence maintained by this set, while preserving
    /// its ordering.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    template <class LOOKUP_KEY>
    typename bsl::enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   LOOKUP_KEY>::value,
        const_iterator>::type
    lower_bound(const LOOKUP_KEY& key) const
    {
        return const_iterator(BloombergLP::bslalg::RbTreeUtil::lowerBound(
            d_tree, this->comparator(), key));
    }

    /// Return an iterator providing non-modifiable access to the first
    /// (i.e., ordered least) `value_type` object in this set greater than
    /// the specified `key`, and the past-the-end iterator if this set does
    /// not contain a `value_type` object greater-than `key`.  Note that
    /// this function returns the *last* position before which a
    /// `value_type` object equivalent to `key` could be inserted into the
    /// ordered sequence maintained by this set, while preserving its
    /// ordering.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    const_iterator upper_bound(const key_type& key) const
    {
        return const_iterator(BloombergLP::bslalg::RbTreeUtil::upperBound(
            d_tree, this->comparator(), key));
    }

    /// Return an iterator providing non-modifiable access to the first
    /// (i.e., ordered least) `value_type` object in this set greater than
    /// the specified `key`, and the past-the-end iterator if this set does
    /// not contain a `value_type` object greater-than `key`.  Note that
    /// this function returns the *last* position before which a
    /// `value_type` object equivalent to `key` could be inserted into the
    /// ordered sequence maintained by this set, while preserving its
    /// ordering.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    template <class LOOKUP_KEY>
    typename bsl::enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   LOOKUP_KEY>::value,
        const_iterator>::type
    upper_bound(const LOOKUP_KEY& key) const
    {
        return const_iterator(BloombergLP::bslalg::RbTreeUtil::upperBound(
            d_tree, this->comparator(), key));
    }

    /// Return a pair of iterators providing non-modifiable access to the
    /// sequence of `value_type` objects in this set that are equivalent to
    /// the specified `key`, where the first iterator is positioned at the
    /// start of the sequence, and the second is positioned one past the end
    /// of the sequence.  The first returned iterator will be
    /// `lower_bound(key)`; the second returned iterator will be
    /// `upper_bound(key)`; and, if this set contains no `value_type`
    /// objects equivalent to `key`, then the two returned iterators will
    /// have the same value.  Note that since a set maintains unique keys,
    /// the range will contain at most one element.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    pair<const_iterator, const_iterator> equal_range(const key_type& key) const
    {
        const_iterator startIt = lower_bound(key);
        const_iterator endIt   = startIt;
        if (endIt != end() && !comparator()(key, *endIt.node())) {
            ++endIt;
        }
        return pair<const_iterator, const_iterator>(startIt, endIt);
    }

    /// Return a pair of iterators providing non-modifiable access to the
    /// sequence of `value_type` objects in this set that are equivalent to
    /// the specified `key`, where the first iterator is positioned at the
    /// start of the sequence, and the second is positioned one past the end
    /// of the sequence.  The first returned iterator will be
    /// `lower_bound(key)`; the second returned iterator will be
    /// `upper_bound(key)`; and, if this set contains no `value_type`
    /// objects equivalent to `key`, then the two returned iterators will
    /// have the same value.  Note that although a set maintains unique
    /// keys, the range may contain more than one element, because a
    /// transparent comparator may have been supplied that provides a
    /// different (but compatible) partitioning of keys for `LOOKUP_KEY` as
    /// the comparisons used to order the keys in the set.
    ///
    /// Note: implemented inline due to Sun CC compilation error.
    template <class LOOKUP_KEY>
    typename bsl::enable_if<
        BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
                                                   LOOKUP_KEY>::value,
        pair<const_iterator, const_iterator> >::type
    equal_range(const LOOKUP_KEY& key) const
    {
        const_iterator startIt = lower_bound(key);
        const_iterator endIt   = startIt;
        if (endIt != end() && !comparator()(key, *endIt.node())) {
            ++endIt;

            // Typically, even with a transparent comparator, we expect to find
            // either 0 or 1 matching keys. We test for those two common cases
            // before performing a logarithmic search via 'upper_bound' to
            // determine the end of the range.

            if (endIt != end() && !comparator()(key, *endIt.node())) {
                endIt = upper_bound(key);
            }
        }
        return pair<const_iterator, const_iterator>(startIt, endIt);
    }

    // BDE_VERIFY pragma: pop
};

#ifdef BSLS_COMPILERFEATURES_SUPPORT_CTAD
// CLASS TEMPLATE DEDUCTION GUIDES

/// Deduce the template parameter `KEY` from the `value_type` of the
/// iterators supplied to the constructor of `set`.  Deduce the template
/// parameters `COMPARATOR` and `ALLOCATOR` from the other parameters passed
/// to the constructor.  This guide does not participate unless the
/// supplied (or defaulted) `ALLOCATOR` meets the requirements of a
/// standard allocator.
template <
    class INPUT_ITERATOR,
    class KEY = typename bsl::iterator_traits<INPUT_ITERATOR>::value_type,
    class COMPARATOR = std::less<KEY>,
    class ALLOCATOR = bsl::allocator<KEY>,
    class = bsl::enable_if_t<!bsl::IsStdAllocator_v<COMPARATOR>>,
    class = bsl::enable_if_t<bsl::IsStdAllocator_v<ALLOCATOR>>
    >
set(INPUT_ITERATOR,
    INPUT_ITERATOR,
    COMPARATOR = COMPARATOR(),
    ALLOCATOR = ALLOCATOR())
-> set<KEY, COMPARATOR, ALLOCATOR>;

/// Deduce the template parameter `KEY` from the `value_type` of the
/// iterators supplied to the constructor of `set`.  Deduce the template
/// parameter `COMPARATOR` from the other parameter passed to the
/// constructor.  This deduction guide does not participate unless the
/// specified `ALLOC` is convertible to `bsl::allocator<KEY>`.
template <
    class INPUT_ITERATOR,
    class COMPARATOR,
    class ALLOC,
    class KEY =
         typename BloombergLP::bslstl::IteratorUtil::IterVal_t<INPUT_ITERATOR>,
    class DEFAULT_ALLOCATOR = bsl::allocator<KEY>,
    class = bsl::enable_if_t<bsl::is_convertible_v<ALLOC *, DEFAULT_ALLOCATOR>>
    >
set(INPUT_ITERATOR, INPUT_ITERATOR, COMPARATOR, ALLOC *)
-> set<KEY, COMPARATOR>;

/// Deduce the template parameter `KEY` from the `value_type` of the
/// iterators supplied to the constructor of `set`.  Deduce the template
/// parameter `ALLOCATOR` from the other parameter passed to the
/// constructor.  This deduction guide does not participate unless the
/// supplied allocator meets the requirements of a standard allocator.
template <
    class INPUT_ITERATOR,
    class ALLOCATOR,
    class KEY =
         typename BloombergLP::bslstl::IteratorUtil::IterVal_t<INPUT_ITERATOR>,
    class = bsl::enable_if_t<bsl::IsStdAllocator_v<ALLOCATOR>>
    >
set(INPUT_ITERATOR, INPUT_ITERATOR, ALLOCATOR)
-> set<KEY, std::less<KEY>, ALLOCATOR>;

/// Deduce the template parameter `KEY` from the `value_type` of the
/// iterators supplied to the constructor of `set`.  This deduction guide
/// does not participate unless the specified `ALLOC` is convertible to
/// `bsl::allocator<KEY>`.
template <
    class INPUT_ITERATOR,
    class ALLOC,
    class KEY =
         typename BloombergLP::bslstl::IteratorUtil::IterVal_t<INPUT_ITERATOR>,
    class DEFAULT_ALLOCATOR = bsl::allocator<KEY>,
    class = bsl::enable_if_t<bsl::is_convertible_v<ALLOC *, DEFAULT_ALLOCATOR>>
    >
set(INPUT_ITERATOR, INPUT_ITERATOR, ALLOC *)
-> set<KEY>;

/// Deduce the template parameter `KEY` from the `value_type` of the
/// initializer_list supplied to the constructor of `set`.  Deduce the
/// template parameters `COMPARATOR` and `ALLOCATOR` from the other
/// parameters passed to the constructor.
template <
    class KEY,
    class COMPARATOR = std::less<KEY>,
    class ALLOCATOR = bsl::allocator<KEY>,
    class = bsl::enable_if_t<!bsl::IsStdAllocator_v<COMPARATOR>>,
    class = bsl::enable_if_t<bsl::IsStdAllocator_v<ALLOCATOR>>
    >
set(std::initializer_list<KEY>,
    COMPARATOR = COMPARATOR(),
    ALLOCATOR = ALLOCATOR())
-> set<KEY, COMPARATOR, ALLOCATOR>;

/// Deduce the template parameter `KEY` from the `value_type` of the
/// initializer_list supplied to the constructor of `set`.  Deduce the
/// template parameter `COMPARATOR` from the other parameter passed to the
/// constructor.  This deduction guide does not participate unless the
/// specified `ALLOC` is convertible to `bsl::allocator<KEY>`.
template <
    class KEY,
    class COMPARATOR,
    class ALLOC,
    class DEFAULT_ALLOCATOR = bsl::allocator<KEY>,
    class = bsl::enable_if_t<bsl::is_convertible_v<ALLOC *, DEFAULT_ALLOCATOR>>
    >
set(std::initializer_list<KEY>, COMPARATOR, ALLOC *)
-> set<KEY, COMPARATOR>;

/// Deduce the template parameter `KEY` from the `value_type` of the
/// initializer_list supplied to the constructor of `set`.  Deduce the
/// template parameter `ALLOCATOR` from the other parameter passed to the
/// constructor.
template <
    class KEY,
    class ALLOCATOR,
    class = bsl::enable_if_t<bsl::IsStdAllocator_v<ALLOCATOR>>
    >
set(std::initializer_list<KEY>, ALLOCATOR)
-> set<KEY, std::less<KEY>, ALLOCATOR>;

/// Deduce the template parameter `KEY` from the `value_type` of the
/// initializer_list supplied to the constructor of `set`.  This deduction
/// guide does not participate unless the specified `ALLOC` is convertible
/// to `bsl::allocator<KEY>`.
template <
    class KEY,
    class ALLOC,
    class DEFAULT_ALLOCATOR = bsl::allocator<KEY>,
    class = bsl::enable_if_t<bsl::is_convertible_v<ALLOC *, DEFAULT_ALLOCATOR>>
    >
set(std::initializer_list<KEY>, ALLOC *)
-> set<KEY>;

#endif

// FREE OPERATORS

/// Return `true` if the specified `lhs` and `rhs` objects have the same
/// value, and `false` otherwise.  Two `set` objects `lhs` and `rhs` have
/// the same value if they have the same number of keys, and each element
/// in the ordered sequence of keys of `lhs` has the same value as the
/// corresponding element in the ordered sequence of keys of `rhs`.  This
/// method requires that the (template parameter) type `KEY` be
/// `equality-comparable` (see {Requirements on `KEY`}).
template <class KEY, class COMPARATOR, class ALLOCATOR>
bool operator==(const set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                const set<KEY, COMPARATOR, ALLOCATOR>& rhs);

#ifndef BSLS_COMPILERFEATURES_SUPPORT_THREE_WAY_COMPARISON
/// Return `true` if the specified `lhs` and `rhs` objects do not have the
/// same value, and `false` otherwise.  Two `set` objects `lhs` and `rhs` do
/// not have the same value if they do not have the same number of keys, or
/// some element in the ordered sequence of keys of `lhs` does not have the
/// same value as the corresponding element in the ordered sequence of keys
/// of `rhs`.  This method requires that the (template parameter) type `KEY`
/// be `equality-comparable` (see {Requirements on `KEY`}).
template <class KEY, class COMPARATOR, class ALLOCATOR>
bool operator!=(const set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                const set<KEY, COMPARATOR, ALLOCATOR>& rhs);
#endif

#ifdef BSLALG_SYNTHTHREEWAYUTIL_AVAILABLE

/// Perform a lexicographic three-way comparison of the specified `lhs` and
/// the specified `rhs` sets by using the comparison operators of `KEY` on
/// each element; return the result of that comparison.
template <class KEY, class COMPARATOR, class ALLOCATOR>
BloombergLP::bslalg::SynthThreeWayUtil::Result<KEY>
operator<=>(const set<KEY, COMPARATOR, ALLOCATOR>& lhs,
            const set<KEY, COMPARATOR, ALLOCATOR>& rhs);

#else

/// Return `true` if the value of the specified `lhs` set is
/// lexicographically less than that of the specified `rhs` set, and `false`
/// otherwise.  Given iterators `i` and `j` over the respective sequences
/// `[lhs.begin() .. lhs.end())` and `[rhs.begin() .. rhs.end())`, the value
/// of set `lhs` is lexicographically less than that of set `rhs` if
/// `true == *i < *j` for the first pair of corresponding iterator positions
/// where `*i < *j` and `*j < *i` are not both `false`.  If no such
/// corresponding iterator position exists, the value of `lhs` is
/// lexicographically less than that of `rhs` if `lhs.size() < rhs.size()`.
/// This method requires that `operator<`, inducing a total order, be
/// defined for `value_type`.
template <class KEY, class COMPARATOR, class ALLOCATOR>
bool operator< (const set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                const set<KEY, COMPARATOR, ALLOCATOR>& rhs);

/// Return `true` if the value of the specified `lhs` set is
/// lexicographically greater than that of the specified `rhs` set, and
/// `false` otherwise.  The value of set `lhs` is lexicographically greater
/// than that of set `rhs` if `rhs` is lexicographically less than `lhs`
/// (see `operator<`).  This method requires that `operator<`, inducing a
/// total order, be defined for `value_type`.  Note that this operator
/// returns `rhs < lhs`.
template <class KEY, class COMPARATOR, class ALLOCATOR>
bool operator> (const set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                const set<KEY, COMPARATOR, ALLOCATOR>& rhs);

/// Return `true` if the value of the specified `lhs` set is
/// lexicographically less than or equal to that of the specified `rhs` set,
/// and `false` otherwise.  The value of set `lhs` is lexicographically less
/// than or equal to that of set `rhs` if `rhs` is not lexicographically
/// less than `lhs` (see `operator<`).  This method requires that
/// `operator<`, inducing a total order, be defined for `value_type`.  Note
/// that this operator returns `!(rhs < lhs)`.
template <class KEY, class COMPARATOR, class ALLOCATOR>
bool operator<=(const set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                const set<KEY, COMPARATOR, ALLOCATOR>& rhs);

/// Return `true` if the value of the specified `lhs` set is
/// lexicographically greater than or equal to that of the specified `rhs`
/// set, and `false` otherwise.  The value of set `lhs` is lexicographically
/// greater than or equal to that of set `rhs` if `lhs` is not
/// lexicographically less than `rhs` (see `operator<`).  This method
/// requires that `operator<`, inducing a total order, be defined for
/// `value_type`.  Note that this operator returns `!(lhs < rhs)`.
template <class KEY, class COMPARATOR, class ALLOCATOR>
bool operator>=(const set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                const set<KEY, COMPARATOR, ALLOCATOR>& rhs);

#endif  // BSLALG_SYNTHTHREEWAYUTIL_AVAILABLE

// FREE FUNCTIONS

/// Erase all the elements in the specified set `s` that satisfy the
/// specified predicate `predicate`.  Return the number of elements erased.
template <class KEY, class COMPARATOR, class ALLOCATOR, class PREDICATE>
typename set<KEY, COMPARATOR, ALLOCATOR>::size_type
erase_if(set<KEY, COMPARATOR, ALLOCATOR>& s, PREDICATE predicate);

/// Exchange the value and comparator of the specified `a` object with those
/// of the specified `b` object; also exchange the allocator of `a` with
/// that of `b` if the (template parameter) type `ALLOCATOR` has the
/// `propagate_on_container_swap` trait, and do not modify either allocator
/// otherwise.  This function provides the no-throw exception-safety
/// guarantee if and only if the (template parameter) type `COMPARATOR`
/// provides a no-throw swap operation, and provides the basic
/// exception-safety guarantee otherwise; if an exception is thrown, both
/// objects are left in valid but unspecified states.  This operation has
/// `O[1]` complexity if either `a` was created with the same allocator as
/// `b` or `ALLOCATOR` has the `propagate_on_container_swap` trait;
/// otherwise, it has `O[n + m]` complexity, where `n` and `m` are the
/// number of elements in `a` and `b`, respectively.  Note that this
/// function`s support for swapping objects created with different
/// allocators when `ALLOCATOR` does not have the
/// `propagate_on_container_swap` trait is a departure from the C++
/// Standard.
template <class KEY, class COMPARATOR, class ALLOCATOR>
void swap(set<KEY, COMPARATOR, ALLOCATOR>& a,
          set<KEY, COMPARATOR, ALLOCATOR>& b)
                                BSLS_KEYWORD_NOEXCEPT_SPECIFICATION(
                                    BSLS_KEYWORD_NOEXCEPT_OPERATOR(a.swap(b)));

// ============================================================================
//                  TEMPLATE AND INLINE FUNCTION DEFINITIONS
// ============================================================================

                             // -----------------
                             // class DataWrapper
                             // -----------------

// CREATORS
template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::DataWrapper::DataWrapper(
                                              const COMPARATOR& comparator,
                                              const ALLOCATOR&  basicAllocator)
: ::bsl::set<KEY, COMPARATOR, ALLOCATOR>::Comparator(comparator)
, d_pool(basicAllocator)
{
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::DataWrapper::DataWrapper(
                          BloombergLP::bslmf::MovableRef<DataWrapper> original)
: ::bsl::set<KEY, COMPARATOR, ALLOCATOR>::Comparator(
                                    MoveUtil::access(original).keyComparator())
, d_pool(MoveUtil::move(MoveUtil::access(original).d_pool))
{
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::NodeFactory&
set<KEY, COMPARATOR, ALLOCATOR>::DataWrapper::nodeFactory()
{
    return d_pool;
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
const typename set<KEY, COMPARATOR, ALLOCATOR>::NodeFactory&
set<KEY, COMPARATOR, ALLOCATOR>::DataWrapper::nodeFactory() const
{
    return d_pool;
}

                             // ---------
                             // class set
                             // ---------

// PRIVATE MANIPULATORS
template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::NodeFactory&
set<KEY, COMPARATOR, ALLOCATOR>::nodeFactory()
{
    return d_compAndAlloc.nodeFactory();
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::Comparator&
set<KEY, COMPARATOR, ALLOCATOR>::comparator()
{
    return d_compAndAlloc;
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
void set<KEY, COMPARATOR, ALLOCATOR>::quickSwapExchangeAllocators(set& other)
{
    BloombergLP::bslalg::RbTreeUtil::swap(&d_tree, &other.d_tree);
    nodeFactory().swapExchangeAllocators(other.nodeFactory());

    // `DataWrapper` contains a `NodeFactory` object and inherits from
    // `Comparator`.  If the empty-base-class optimization has been applied to
    // `Comparator`, then we must not call `swap` on it because
    // `sizeof(Comparator) > 0` and, therefore, we will incorrectly swap bytes
    // of the `NodeFactory` members!

    if (sizeof(NodeFactory) != sizeof(DataWrapper)) {
        comparator().swap(other.comparator());
    }
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
void set<KEY, COMPARATOR, ALLOCATOR>::quickSwapRetainAllocators(set& other)
{
    BloombergLP::bslalg::RbTreeUtil::swap(&d_tree, &other.d_tree);
    nodeFactory().swapRetainAllocators(other.nodeFactory());

    // See `quickSwapExchangeAllocators` (above).

    if (sizeof(NodeFactory) != sizeof(DataWrapper)) {
        comparator().swap(other.comparator());
    }
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
template <class INPUT_ITERATOR, class SENTINEL>
inline
void set<KEY, COMPARATOR, ALLOCATOR>::constructFromRange(INPUT_ITERATOR first,
                                                         SENTINEL       last)
{
    if (first == last) {
        return;                                                       // RETURN
    }

    if BSLS_KEYWORD_CONSTEXPR_CPP17 (
        BloombergLP::bslstl::IteratorUtil::
                      canCalculateInsertDistance<INPUT_ITERATOR, SENTINEL>()) {
        const size_type numElements = static_cast<size_type>(
            BloombergLP::bslstl::IteratorUtil::insertDistance(first, last));
        nodeFactory().reserveNodes(numElements);
    }

    BloombergLP::bslalg::RbTreeUtilTreeProctor<NodeFactory> proctor(
                                                               &d_tree,
                                                               &nodeFactory());

    // The following loop guarantees amortized linear time to insert an ordered
    // sequence of values (as required by the standard).   If the values are
    // in sorted order, we are guaranteed the next node can be inserted as the
    // right child of the previous node, and can call 'insertAt' without
    // 'findUniqueInsertLocation'.

    insert(*first);
    BloombergLP::bslalg::RbTreeNode *prevNode = d_tree.rootNode();

    while (++first != last) {

        const value_type& value = *first;
        if (this->comparator()(value, *prevNode)) {
            // The values are not in order, so insert them normally.
            insert(value);
            insertFromRange(++first, last);
            break;
        }

        if (this->comparator()(*prevNode, value)) {
            BloombergLP::bslalg::RbTreeNode *node =
                                   nodeFactory().emplaceIntoNewNode(value);
            BloombergLP::bslalg::RbTreeUtil::insertAt(&d_tree,
                                                      prevNode,
                                                      false,
                                                      node);
            prevNode = node;
        }
    }

    proctor.release();
}

#if defined(BSLS_LIBRARYFEATURES_HAS_CPP20_CONCEPTS) \
 && defined(BSLS_LIBRARYFEATURES_HAS_CPP20_RANGES)

template <class KEY, class COMPARATOR, class ALLOCATOR>
template <class INPUT_ITERATOR, class SENTINEL>
inline
void set<KEY, COMPARATOR, ALLOCATOR>::constructFromRange(
                                                    INPUT_ITERATOR first,
                                                    SENTINEL       last,
                                                    size_t         numElements)

{
    BSLS_ASSERT_SAFE((
        !BloombergLP::bslstl::IteratorUtil
                       ::canCalculateInsertDistance<INPUT_ITERATOR, SENTINEL>()
        || numElements == static_cast<size_type>(
             BloombergLP::bslstl::IteratorUtil::insertDistance(first, last))));

    if (first == last) {
        return;                                                       // RETURN
    }

    if (0 < numElements) {
        nodeFactory().reserveNodes(numElements);
    }

    BloombergLP::bslalg::RbTreeUtilTreeProctor<NodeFactory> proctor(
                                                               &d_tree,
                                                               &nodeFactory());

    // The following loop guarantees amortized linear time to insert an ordered
    // sequence of values (as required by the standard).   If the values are
    // in sorted order, we are guaranteed the next node can be inserted as the
    // right child of the previous node, and can call 'insertAt' without
    // 'findUniqueInsertLocation'.

    insert(*first); --numElements;
    BloombergLP::bslalg::RbTreeNode *prevNode = d_tree.rootNode();

    while (++first != last) {

        const value_type& value = *first;
        if (this->comparator()(value, *prevNode)) {
            // The values are not in order, so insert them normally.
            insert(value); --numElements;
            insertFromRange(++first, last, numElements);
            break;
        }

        if (this->comparator()(*prevNode, value)) {
            BloombergLP::bslalg::RbTreeNode *node =
                                   nodeFactory().emplaceIntoNewNode(value);
            BloombergLP::bslalg::RbTreeUtil::insertAt(&d_tree,
                                                      prevNode,
                                                      false,
                                                      node);
            --numElements;
            prevNode = node;
        }
    }

    proctor.release();
}

#endif

template <class KEY, class COMPARATOR, class ALLOCATOR>
template <class INPUT_ITERATOR, class SENTINEL>
inline
void set<KEY, COMPARATOR, ALLOCATOR>::insertFromRange(INPUT_ITERATOR first,
                                                      SENTINEL       last)
{
    ///Implementation Notes
    ///--------------------
    // First, consume currently held free nodes.  Free nodes may be available
    // from previous insertions that where skipped due to collisions with
    // keys already in the map or from nodes reserved in `constructFromRange`.
    //
    // If those nodes are insufficient *and* one can calculate the remaining
    // number of elements, then reserve exactly that many free nodes.  There is
    // no more than one call to 'reserveNodes' per invocation of this method,
    // hence the use of 'BSLS_PERFORMANCEHINT_PREDICT_UNLIKELY'.
    //
    // When reserving nodes, we assume the elements remaining to be inserted
    // have unique keys that do not duplicate any keys already in the container
    // If there are any duplicates, this container will have free nodes on
    // return from this method.

    while (first != last) {

        if (BloombergLP::bslstl::IteratorUtil
                       ::canCalculateInsertDistance<INPUT_ITERATOR, SENTINEL>()
        && BSLS_PERFORMANCEHINT_PREDICT_UNLIKELY(
                                              !nodeFactory().hasFreeNodes())) {
            nodeFactory().reserveNodes(
               BloombergLP::bslstl::IteratorUtil::insertDistance(first, last));
        }

        insert(*first);
        ++first;
    }
}

#if defined(BSLS_LIBRARYFEATURES_HAS_CPP20_CONCEPTS) \
 && defined(BSLS_LIBRARYFEATURES_HAS_CPP20_RANGES)

template <class KEY, class COMPARATOR, class ALLOCATOR>
template <class INPUT_ITERATOR, class SENTINEL>
inline
void set<KEY, COMPARATOR, ALLOCATOR>::insertFromRange(
                                                    INPUT_ITERATOR first,
                                                    SENTINEL       last,
                                                    size_t         numElements)
{
    BSLS_ASSERT_SAFE((
        !BloombergLP::bslstl::IteratorUtil
                       ::canCalculateInsertDistance<INPUT_ITERATOR, SENTINEL>()
        || numElements == static_cast<size_type>(
             BloombergLP::bslstl::IteratorUtil::insertDistance(first, last))));

    while (first != last) {

        if (BSLS_PERFORMANCEHINT_PREDICT_UNLIKELY(
                                              !nodeFactory().hasFreeNodes())) {
            nodeFactory().reserveNodes(numElements);
        }

        insert(*first);
        --numElements;
        ++first;
    }
}

#endif

// PRIVATE ACCESSORS
template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
const typename set<KEY, COMPARATOR, ALLOCATOR>::NodeFactory&
set<KEY, COMPARATOR, ALLOCATOR>::nodeFactory() const
{
    return d_compAndAlloc.nodeFactory();
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
const typename set<KEY, COMPARATOR, ALLOCATOR>::Comparator&
set<KEY, COMPARATOR, ALLOCATOR>::comparator() const
{
    return d_compAndAlloc;
}

// CREATORS
template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::set()
: d_compAndAlloc(COMPARATOR(), ALLOCATOR())
, d_tree()
{
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::set(const ALLOCATOR& basicAllocator)
: d_compAndAlloc(COMPARATOR(), basicAllocator)
, d_tree()
{
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::set(const set& original)
: d_compAndAlloc(original.comparator().keyComparator(),
                 AllocatorTraits::select_on_container_copy_construction(
                                          original.nodeFactory().allocator()))
, d_tree()
{
    if (0 < original.size()) {
        nodeFactory().reserveNodes(original.size());
        BloombergLP::bslalg::RbTreeUtil::copyTree(&d_tree,
                                                  original.d_tree,
                                                  &nodeFactory());
    }
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::set(
                                  BloombergLP::bslmf::MovableRef<set> original)
: d_compAndAlloc(MoveUtil::move(MoveUtil::access(original).d_compAndAlloc))
, d_tree()
{
    set& lvalue = original;
    BloombergLP::bslalg::RbTreeUtil::swap(&d_tree, &lvalue.d_tree);
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::set(
                 const set&                                     original,
                 const typename type_identity<ALLOCATOR>::type& basicAllocator)
: d_compAndAlloc(original.comparator().keyComparator(), basicAllocator)
, d_tree()
{
    if (0 < original.size()) {
        nodeFactory().reserveNodes(original.size());
        BloombergLP::bslalg::RbTreeUtil::copyTree(&d_tree,
                                                  original.d_tree,
                                                  &nodeFactory());
    }
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::set(
                 BloombergLP::bslmf::MovableRef<set>            original,
                 const typename type_identity<ALLOCATOR>::type& basicAllocator)
: d_compAndAlloc(MoveUtil::access(original).comparator().keyComparator(),
                 basicAllocator)
, d_tree()
{
    set& lvalue = original;

    if (BSLS_PERFORMANCEHINT_PREDICT_LIKELY(
              nodeFactory().allocator() == lvalue.nodeFactory().allocator())) {
        d_compAndAlloc.nodeFactory().adopt(
                          MoveUtil::move(lvalue.d_compAndAlloc.nodeFactory()));
        BloombergLP::bslalg::RbTreeUtil::swap(&d_tree, &lvalue.d_tree);
    }
    else {
        if (0 < lvalue.size()) {
            nodeFactory().reserveNodes(lvalue.size());
            BloombergLP::bslalg::RbTreeUtil::moveTree(&d_tree,
                                                      &lvalue.d_tree,
                                                      &nodeFactory(),
                                                      &lvalue.nodeFactory());
        }
    }
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
template <class INPUT_ITERATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::set(INPUT_ITERATOR    first,
                                     INPUT_ITERATOR    last,
                                     const COMPARATOR& comparator,
                                     const ALLOCATOR&  basicAllocator)
: d_compAndAlloc(comparator, basicAllocator)
, d_tree()
{
    if (first != last) {

        const size_type numElements = static_cast<size_type>(
            BloombergLP::bslstl::IteratorUtil::insertDistance(first, last));

        if (0 < numElements) {
            nodeFactory().reserveNodes(numElements);
        }

        BloombergLP::bslalg::RbTreeUtilTreeProctor<NodeFactory> proctor(
                                                               &d_tree,
                                                               &nodeFactory());

        // The following loop guarantees amortized linear time to insert an
        // ordered sequence of values (as required by the standard).   If the
        // values are in sorted order, we are guaranteed the next node can be
        // inserted as the right child of the previous node, and can call
        // `insertAt` without `findUniqueInsertLocation`.

        insert(*first);
        BloombergLP::bslalg::RbTreeNode *prevNode = d_tree.rootNode();
        while (++first != last) {
            // The values are not in order, so insert them normally.

            const value_type& value = *first;
            if (this->comparator()(value, *prevNode)) {
                insert(value);
                insert(++first, last);
                break;
            }

            if (this->comparator()(*prevNode, value)) {
                BloombergLP::bslalg::RbTreeNode *node =
                                       nodeFactory().emplaceIntoNewNode(value);
                BloombergLP::bslalg::RbTreeUtil::insertAt(&d_tree,
                                                          prevNode,
                                                          false,
                                                          node);
                prevNode = node;
            }
        }

        proctor.release();
    }
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
template <class INPUT_ITERATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::set(INPUT_ITERATOR    first,
                                     INPUT_ITERATOR    last,
                                     const ALLOCATOR&  basicAllocator)
: d_compAndAlloc(COMPARATOR(), basicAllocator)
, d_tree()
{
    if (first != last) {

        const size_type numElements = static_cast<size_type>(
            BloombergLP::bslstl::IteratorUtil::insertDistance(first, last));

        if (0 < numElements) {
            nodeFactory().reserveNodes(numElements);
        }

        BloombergLP::bslalg::RbTreeUtilTreeProctor<NodeFactory> proctor(
                                                               &d_tree,
                                                               &nodeFactory());

        // The following loop guarantees amortized linear time to insert an
        // ordered sequence of values (as required by the standard).   If the
        // values are in sorted order, we are guaranteed the next node can be
        // inserted as the right child of the previous node, and can call
        // `insertAt` without `findUniqueInsertLocation`.

        insert(*first);
        BloombergLP::bslalg::RbTreeNode *prevNode = d_tree.rootNode();
        while (++first != last) {
            // The values are not in order, so insert them normally.

            const value_type& value = *first;
            if (this->comparator()(value, *prevNode)) {
                insert(value);
                insert(++first, last);
                break;
            }

            if (this->comparator()(*prevNode, value)) {
                BloombergLP::bslalg::RbTreeNode *node =
                                       nodeFactory().emplaceIntoNewNode(value);
                BloombergLP::bslalg::RbTreeUtil::insertAt(&d_tree,
                                                          prevNode,
                                                          false,
                                                          node);
                prevNode = node;
            }
        }

        proctor.release();
    }
}

#if defined(BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS)
template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::set(std::initializer_list<KEY> values,
                                     const COMPARATOR&          comparator,
                                     const ALLOCATOR&           basicAllocator)
: set(values.begin(), values.end(), comparator, basicAllocator)
{
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::set(std::initializer_list<KEY> values,
                                     const ALLOCATOR&           basicAllocator)
: set(values.begin(), values.end(), COMPARATOR(), basicAllocator)
{
}
#endif

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>::~set()
{
    clear();
}

// MANIPULATORS
template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>&
set<KEY, COMPARATOR, ALLOCATOR>::operator=(const set& rhs)
{
    if (BSLS_PERFORMANCEHINT_PREDICT_LIKELY(this != &rhs)) {
        if (AllocatorTraits::propagate_on_container_copy_assignment::value) {
            set other(rhs, rhs.nodeFactory().allocator());
            quickSwapExchangeAllocators(other);
        }
        else {
            set other(rhs, nodeFactory().allocator());
            quickSwapRetainAllocators(other);
        }
    }
    return *this;
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>&
set<KEY, COMPARATOR, ALLOCATOR>::operator=(
                                       BloombergLP::bslmf::MovableRef<set> rhs)
                        BSLS_KEYWORD_NOEXCEPT_SPECIFICATION(
                            AllocatorTraits::is_always_equal::value
                         && std::is_nothrow_move_assignable<COMPARATOR>::value)
{
    set& lvalue = rhs;

    if (BSLS_PERFORMANCEHINT_PREDICT_LIKELY(this != &lvalue)) {
        if (nodeFactory().allocator() == lvalue.nodeFactory().allocator()) {
            set other(MoveUtil::move(lvalue));
            quickSwapRetainAllocators(other);
        }
        else if (
              AllocatorTraits::propagate_on_container_move_assignment::value) {
            set other(MoveUtil::move(lvalue));
            quickSwapExchangeAllocators(other);
        }
        else {
            set other(MoveUtil::move(lvalue), nodeFactory().allocator());
            quickSwapRetainAllocators(other);
        }
    }
    return *this;
}

#if defined(BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS)
template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
set<KEY, COMPARATOR, ALLOCATOR>&
set<KEY, COMPARATOR, ALLOCATOR>::operator=(std::initializer_list<KEY> values)
{
    clear();
    insert(values.begin(), values.end());
    return *this;
}
#endif

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::iterator
set<KEY, COMPARATOR, ALLOCATOR>::begin() BSLS_KEYWORD_NOEXCEPT
{
    return iterator(d_tree.firstNode());
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::iterator
set<KEY, COMPARATOR, ALLOCATOR>::end() BSLS_KEYWORD_NOEXCEPT
{
    return iterator(d_tree.sentinel());
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::reverse_iterator
set<KEY, COMPARATOR, ALLOCATOR>::rbegin() BSLS_KEYWORD_NOEXCEPT
{
    return reverse_iterator(end());
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::reverse_iterator
set<KEY, COMPARATOR, ALLOCATOR>::rend() BSLS_KEYWORD_NOEXCEPT
{
    return reverse_iterator(begin());
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
pair<typename set<KEY, COMPARATOR, ALLOCATOR>::iterator, bool>
set<KEY, COMPARATOR, ALLOCATOR>::insert(const value_type& value)
{
    int comparisonResult;
    BloombergLP::bslalg::RbTreeNode *insertLocation =
        BloombergLP::bslalg::RbTreeUtil::findUniqueInsertLocation(
                                                            &comparisonResult,
                                                            &d_tree,
                                                            this->comparator(),
                                                            value);
    if (!comparisonResult) {
        return pair<iterator, bool>(iterator(insertLocation), false);
                                                                      // RETURN
    }
    BloombergLP::bslalg::RbTreeNode *node =
                                       nodeFactory().emplaceIntoNewNode(value);
    BloombergLP::bslalg::RbTreeUtil::insertAt(&d_tree,
                                              insertLocation,
                                              comparisonResult < 0,
                                              node);
    return pair<iterator, bool>(iterator(node), true);
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
pair<typename set<KEY, COMPARATOR, ALLOCATOR>::iterator, bool>
set<KEY, COMPARATOR, ALLOCATOR>::insert(
                              BloombergLP::bslmf::MovableRef<value_type> value)
{
    value_type& lvalue = value;
    int comparisonResult;
    BloombergLP::bslalg::RbTreeNode *insertLocation =
        BloombergLP::bslalg::RbTreeUtil::findUniqueInsertLocation(
                                                            &comparisonResult,
                                                            &d_tree,
                                                            this->comparator(),
                                                            lvalue);
    if (!comparisonResult) {
        return pair<iterator, bool>(iterator(insertLocation), false);
                                                                      // RETURN
    }
    BloombergLP::bslalg::RbTreeNode *node =
                      nodeFactory().emplaceIntoNewNode(MoveUtil::move(lvalue));
    BloombergLP::bslalg::RbTreeUtil::insertAt(&d_tree,
                                              insertLocation,
                                              comparisonResult < 0,
                                              node);
    return pair<iterator, bool>(iterator(node), true);
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::iterator
set<KEY, COMPARATOR, ALLOCATOR>::insert(const_iterator    hint,
                                        const value_type& value)
{
    BloombergLP::bslalg::RbTreeNode *hintNode =
                const_cast<BloombergLP::bslalg::RbTreeNode *>(hint.node());
    int comparisonResult;
    BloombergLP::bslalg::RbTreeNode *insertLocation =
        BloombergLP::bslalg::RbTreeUtil::findUniqueInsertLocation(
                                                            &comparisonResult,
                                                            &d_tree,
                                                            this->comparator(),
                                                            value,
                                                            hintNode);
    if (!comparisonResult) {
        return iterator(insertLocation);                              // RETURN
    }

    BloombergLP::bslalg::RbTreeNode *node =
                                       nodeFactory().emplaceIntoNewNode(value);
    BloombergLP::bslalg::RbTreeUtil::insertAt(&d_tree,
                                              insertLocation,
                                              comparisonResult < 0,
                                              node);
    return iterator(node);
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::iterator
set<KEY, COMPARATOR, ALLOCATOR>::insert(const_iterator    hint,
                              BloombergLP::bslmf::MovableRef<value_type> value)
{
    value_type& lvalue = value;
    BloombergLP::bslalg::RbTreeNode *hintNode =
                const_cast<BloombergLP::bslalg::RbTreeNode *>(hint.node());
    int comparisonResult;
    BloombergLP::bslalg::RbTreeNode *insertLocation =
        BloombergLP::bslalg::RbTreeUtil::findUniqueInsertLocation(
                                                            &comparisonResult,
                                                            &d_tree,
                                                            this->comparator(),
                                                            lvalue,
                                                            hintNode);
    if (!comparisonResult) {
        return iterator(insertLocation);                              // RETURN
    }

    BloombergLP::bslalg::RbTreeNode *node =
                      nodeFactory().emplaceIntoNewNode(MoveUtil::move(lvalue));

    BloombergLP::bslalg::RbTreeUtil::insertAt(&d_tree,
                                              insertLocation,
                                              comparisonResult < 0,
                                              node);
    return iterator(node);
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
template <class INPUT_ITERATOR>
inline
void set<KEY, COMPARATOR, ALLOCATOR>::insert(INPUT_ITERATOR first,
                                             INPUT_ITERATOR last)
{
    ///Implementation Notes
    ///--------------------
    // First, consume currently held free nodes.  If those nodes are
    // insufficient *and* one can calculate the remaining number of elements,
    // then reserve exactly that many free nodes.  There is no more than one
    // call to `reserveNodes` per invocation of this method, hence the use of
    // `BSLS_PERFORMANCEHINT_PREDICT_UNLIKELY`.  When reserving nodes, we
    // assume the elements remaining to be inserted are unique and do not
    // duplicate any elements already in the container.  If there are any
    // duplicates, this container will have free nodes on return from this
    // method.

    while (first != last) {
        if (BloombergLP::bslstl::IteratorUtil::
                    canCalculateInsertDistance<INPUT_ITERATOR,INPUT_ITERATOR>()
        && BSLS_PERFORMANCEHINT_PREDICT_UNLIKELY(
                                              !nodeFactory().hasFreeNodes())) {
            const size_type numElements = static_cast<size_type>(
               BloombergLP::bslstl::IteratorUtil::insertDistance(first, last));
            nodeFactory().reserveNodes(numElements);
        }
        insert(*first);
        ++first;
    }
}

#if defined(BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS)
template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
void set<KEY, COMPARATOR, ALLOCATOR>::insert(std::initializer_list<KEY> values)
{
    insert(values.begin(), values.end());
}
#endif

#if !BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES
template <class KEY, class COMPARATOR, class ALLOCATOR>
template <class... Args>
inline
pair<typename set<KEY, COMPARATOR, ALLOCATOR>::iterator, bool>
set<KEY, COMPARATOR, ALLOCATOR>::emplace(Args&&... arguments)
{
    BloombergLP::bslalg::RbTreeNode *node = nodeFactory().emplaceIntoNewNode(
        BSLS_COMPILERFEATURES_FORWARD(Args, arguments)...);
    int comparisonResult;
    BloombergLP::bslalg::RbTreeNode *insertLocation =
        BloombergLP::bslalg::RbTreeUtil::findUniqueInsertLocation(
                                     &comparisonResult,
                                     &d_tree,
                                     this->comparator(),
                                     static_cast<const Node *>(node)->value());
    if (!comparisonResult) {
        nodeFactory().deleteNode(node);
        return pair<iterator, bool>(iterator(insertLocation), false);
                                                                      // RETURN
    }
    BloombergLP::bslalg::RbTreeUtil::insertAt(&d_tree,
                                              insertLocation,
                                              comparisonResult < 0,
                                              node);
    return pair<iterator, bool>(iterator(node), true);
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
template <class... Args>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::iterator
set<KEY, COMPARATOR, ALLOCATOR>::emplace_hint(const_iterator hint,
                                              Args&&...      arguments)
{
    BloombergLP::bslalg::RbTreeNode *node = nodeFactory().emplaceIntoNewNode(
        BSLS_COMPILERFEATURES_FORWARD(Args, arguments)...);
    BloombergLP::bslalg::RbTreeNode *hintNode =
                const_cast<BloombergLP::bslalg::RbTreeNode *>(hint.node());
    int comparisonResult;
    BloombergLP::bslalg::RbTreeNode *insertLocation =
        BloombergLP::bslalg::RbTreeUtil::findUniqueInsertLocation(
                                                            &comparisonResult,
                                                            &d_tree,
                                                            this->comparator(),
                                      static_cast<const Node *>(node)->value(),
                                                            hintNode);
    if (!comparisonResult) {
        nodeFactory().deleteNode(node);
        return iterator(insertLocation);                              // RETURN
    }

    BloombergLP::bslalg::RbTreeUtil::insertAt(&d_tree,
                                              insertLocation,
                                              comparisonResult < 0,
                                              node);
    return iterator(node);
}
#endif

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::iterator
set<KEY, COMPARATOR, ALLOCATOR>::erase(const_iterator position)
{
    BSLS_ASSERT_SAFE(position != end());

    BloombergLP::bslalg::RbTreeNode *node =
                const_cast<BloombergLP::bslalg::RbTreeNode *>(position.node());
    BloombergLP::bslalg::RbTreeNode *result =
                                   BloombergLP::bslalg::RbTreeUtil::next(node);
    BloombergLP::bslalg::RbTreeUtil::remove(&d_tree, node);
    nodeFactory().deleteNode(node);
    return iterator(result);
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::size_type
set<KEY, COMPARATOR, ALLOCATOR>::erase(const key_type& key)
{
    const_iterator it = find(key);
    if (it == end()) {
        return 0;                                                     // RETURN
    }
    erase(it);
    return 1;
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::iterator
set<KEY, COMPARATOR, ALLOCATOR>::erase(const_iterator first,
                                       const_iterator last)
{
    while (first != last) {
        first = erase(first);
    }
    return iterator(last.node());
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
void set<KEY, COMPARATOR, ALLOCATOR>::swap(set& other)
                              BSLS_KEYWORD_NOEXCEPT_SPECIFICATION(
                                  AllocatorTraits::is_always_equal::value
                               && bsl::is_nothrow_swappable<COMPARATOR>::value)
{
    if (AllocatorTraits::propagate_on_container_swap::value) {
        quickSwapExchangeAllocators(other);
    }
    else {
        // C++11 behavior for member `swap`: undefined for unequal allocators.
        // BSLS_ASSERT(allocator() == other.allocator());

        if (BSLS_PERFORMANCEHINT_PREDICT_LIKELY(
               nodeFactory().allocator() == other.nodeFactory().allocator())) {
            quickSwapRetainAllocators(other);
        }
        else {
            BSLS_PERFORMANCEHINT_UNLIKELY_HINT;

            set toOtherCopy(MoveUtil::move(*this),
                            other.nodeFactory().allocator());
            set toThisCopy(MoveUtil::move(other), nodeFactory().allocator());

            this->quickSwapRetainAllocators(toThisCopy);
            other.quickSwapRetainAllocators(toOtherCopy);
        }
    }
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
void set<KEY, COMPARATOR, ALLOCATOR>::clear() BSLS_KEYWORD_NOEXCEPT
{
    BSLS_ASSERT_SAFE(d_tree.firstNode());

    if (d_tree.rootNode()) {
        BSLS_ASSERT_SAFE(0 < d_tree.numNodes());
        BSLS_ASSERT_SAFE(d_tree.firstNode() != d_tree.sentinel());

        BloombergLP::bslalg::RbTreeUtil::deleteTree(&d_tree, &nodeFactory());
    }
#if defined(BSLS_ASSERT_SAFE_IS_USED)
    else {
        BSLS_ASSERT_SAFE(0 == d_tree.numNodes());
        BSLS_ASSERT_SAFE(d_tree.firstNode() == d_tree.sentinel());
    }
#endif
}

// ACCESSORS
template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::allocator_type
set<KEY, COMPARATOR, ALLOCATOR>::get_allocator() const BSLS_KEYWORD_NOEXCEPT
{
    return nodeFactory().allocator();
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::const_iterator
set<KEY, COMPARATOR, ALLOCATOR>::begin() const BSLS_KEYWORD_NOEXCEPT
{
    return cbegin();
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::const_iterator
set<KEY, COMPARATOR, ALLOCATOR>::end() const BSLS_KEYWORD_NOEXCEPT
{
    return cend();
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::const_reverse_iterator
set<KEY, COMPARATOR, ALLOCATOR>::rbegin() const BSLS_KEYWORD_NOEXCEPT
{
    return crbegin();
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::const_reverse_iterator
set<KEY, COMPARATOR, ALLOCATOR>::rend() const BSLS_KEYWORD_NOEXCEPT
{
    return crend();
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::const_iterator
set<KEY, COMPARATOR, ALLOCATOR>::cbegin() const BSLS_KEYWORD_NOEXCEPT
{
    return const_iterator(d_tree.firstNode());
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::const_iterator
set<KEY, COMPARATOR, ALLOCATOR>::cend() const BSLS_KEYWORD_NOEXCEPT
{
    return const_iterator(d_tree.sentinel());
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::const_reverse_iterator
set<KEY, COMPARATOR, ALLOCATOR>::crbegin() const BSLS_KEYWORD_NOEXCEPT
{
    return const_reverse_iterator(end());
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::const_reverse_iterator
set<KEY, COMPARATOR, ALLOCATOR>::crend() const BSLS_KEYWORD_NOEXCEPT
{
    return const_reverse_iterator(begin());
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
bool set<KEY, COMPARATOR, ALLOCATOR>::contains(const key_type& key) const
{
    return find(key) != end();
}

// capacity:
template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
bool set<KEY, COMPARATOR, ALLOCATOR>::empty() const BSLS_KEYWORD_NOEXCEPT
{
    return 0 == d_tree.numNodes();
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::size_type
set<KEY, COMPARATOR, ALLOCATOR>::size() const BSLS_KEYWORD_NOEXCEPT
{
    return d_tree.numNodes();
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::size_type
set<KEY, COMPARATOR, ALLOCATOR>::max_size() const BSLS_KEYWORD_NOEXCEPT
{
    return AllocatorTraits::max_size(get_allocator());
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::key_compare
set<KEY, COMPARATOR, ALLOCATOR>::key_comp() const
{
    return comparator().keyComparator();
}

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
typename set<KEY, COMPARATOR, ALLOCATOR>::value_compare
set<KEY, COMPARATOR, ALLOCATOR>::value_comp() const
{
    return value_compare(key_comp());
}

}  // close namespace bsl

// FREE OPERATORS
template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
bool bsl::operator==(const bsl::set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                     const bsl::set<KEY, COMPARATOR, ALLOCATOR>& rhs)
{
    return BloombergLP::bslalg::RangeCompare::equal(lhs.begin(),
                                                    lhs.end(),
                                                    lhs.size(),
                                                    rhs.begin(),
                                                    rhs.end(),
                                                    rhs.size());
}

#ifndef BSLS_COMPILERFEATURES_SUPPORT_THREE_WAY_COMPARISON
template <class KEY,  class COMPARATOR,  class ALLOCATOR>
inline
bool bsl::operator!=(const bsl::set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                     const bsl::set<KEY, COMPARATOR, ALLOCATOR>& rhs)
{
    return !(lhs == rhs);
}
#endif

#ifdef BSLALG_SYNTHTHREEWAYUTIL_AVAILABLE

template <class KEY, class COMPARATOR, class ALLOCATOR>
inline
BloombergLP::bslalg::SynthThreeWayUtil::Result<KEY>
bsl::operator<=>(const set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                 const set<KEY, COMPARATOR, ALLOCATOR>& rhs)
{
    return bsl::lexicographical_compare_three_way(
                              lhs.begin(),
                              lhs.end(),
                              rhs.begin(),
                              rhs.end(),
                              BloombergLP::bslalg::SynthThreeWayUtil::compare);
}

#else

template <class KEY,  class COMPARATOR,  class ALLOCATOR>
inline
bool bsl::operator<(const bsl::set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                    const bsl::set<KEY, COMPARATOR, ALLOCATOR>& rhs)
{
    return 0 > BloombergLP::bslalg::RangeCompare::lexicographical(lhs.begin(),
                                                                  lhs.end(),
                                                                  lhs.size(),
                                                                  rhs.begin(),
                                                                  rhs.end(),
                                                                  rhs.size());
}

template <class KEY,  class COMPARATOR,  class ALLOCATOR>
inline
bool bsl::operator>(const bsl::set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                    const bsl::set<KEY, COMPARATOR, ALLOCATOR>& rhs)
{
    return rhs < lhs;
}

template <class KEY,  class COMPARATOR,  class ALLOCATOR>
inline
bool bsl::operator<=(const bsl::set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                     const bsl::set<KEY, COMPARATOR, ALLOCATOR>& rhs)
{
    return !(rhs < lhs);
}

template <class KEY,  class COMPARATOR,  class ALLOCATOR>
inline
bool bsl::operator>=(const bsl::set<KEY, COMPARATOR, ALLOCATOR>& lhs,
                     const bsl::set<KEY, COMPARATOR, ALLOCATOR>& rhs)
{
    return !(lhs < rhs);
}

#endif  // BSLALG_SYNTHTHREEWAYUTIL_AVAILABLE

// FREE FUNCTIONS
template <class KEY,  class COMPARATOR,  class ALLOCATOR, class PREDICATE>
inline
typename bsl::set<KEY, COMPARATOR, ALLOCATOR>::size_type
bsl::erase_if(set<KEY, COMPARATOR, ALLOCATOR>& s, PREDICATE predicate)
{
    return BloombergLP::bslstl::AlgorithmUtil::containerEraseIf(s, predicate);
}

template <class KEY,  class COMPARATOR,  class ALLOCATOR>
inline
void bsl::swap(bsl::set<KEY, COMPARATOR, ALLOCATOR>& a,
               bsl::set<KEY, COMPARATOR, ALLOCATOR>& b)
                                 BSLS_KEYWORD_NOEXCEPT_SPECIFICATION(
                                     BSLS_KEYWORD_NOEXCEPT_OPERATOR(a.swap(b)))
{
    a.swap(b);
}

// ============================================================================
//                                TYPE TRAITS
// ============================================================================

// Type traits for STL *ordered* containers:
//: o An ordered container defines STL iterators.
//: o An ordered container uses 'bslma' allocators if the (template parameter)
//:   type 'ALLOCATOR' is convertible from 'bslma::Allocator*'.

namespace BloombergLP {

namespace bslalg {

template <class KEY,  class COMPARATOR,  class ALLOCATOR>
struct HasStlIterators<bsl::set<KEY, COMPARATOR, ALLOCATOR> >
    : bsl::true_type
{};

}  // close namespace bslalg

namespace bslma {

template <class KEY,  class COMPARATOR,  class ALLOCATOR>
struct UsesBslmaAllocator<bsl::set<KEY, COMPARATOR, ALLOCATOR> >
    : bsl::is_convertible<Allocator*, ALLOCATOR>
{};

}  // close namespace bslma

}  // close enterprise namespace

#endif // End C++11 code

#endif

// ----------------------------------------------------------------------------
// Copyright 2019 Bloomberg Finance L.P.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------- END-OF-FILE ----------------------------------
