/*!
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@file
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Forward declares `boost::hana::set`.
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@copyright Louis Dionne 2013-2017
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_FWD_SET_HPP
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#define BOOST_HANA_FWD_SET_HPP
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#include <boost/hana/config.hpp>
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#include <boost/hana/fwd/core/to.hpp>
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#include <boost/hana/fwd/core/make.hpp>
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#include <boost/hana/fwd/erase_key.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @ingroup group-datatypes
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//! Basic unordered container requiring unique, `Comparable` and
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//! `Hashable` keys.
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//!
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//! A set is an unordered container that can hold heterogeneous keys.
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//! A set requires (and ensures) that no duplicates are present when
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//! inserting new keys.
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//!
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//! @note
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//! The actual representation of a `hana::set` is implementation-defined.
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//! In particular, one should not take for granted the order of the
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//! template parameters and the presence of any additional constructors
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//! or assignment operators than what is documented. The canonical way of
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//! creating a `hana::set` is through `hana::make_set`. More details
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//! [in the tutorial](@ref tutorial-containers-types).
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//!
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//!
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//! Modeled concepts
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//! ----------------
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//! 1. `Comparable`\n
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//! Two sets are equal iff they contain the same elements, regardless of
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//! the order.
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//! @include example/set/comparable.cpp
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//!
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//! 2. Foldable\n
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//! Folding a set is equivalent to folding the sequence of its values.
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//! However, note that the values are not required to be in any specific
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//! order, so using the folds provided here with an operation that is not
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//! both commutative and associative will yield non-deterministic behavior.
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//! @include example/set/foldable.cpp
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//!
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//! 3. Searchable\n
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//! The elements in a set act as both its keys and its values. Since the
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//! elements of a set are unique, searching for an element will return
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//! either the only element which is equal to the searched value, or
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//! `nothing`. Also note that `operator[]` can be used instead of the
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//! `at_key` function.
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//! @include example/set/searchable.cpp
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//!
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//!
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//! Conversion from any `Foldable`
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//! ------------------------------
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//! Any `Foldable` structure can be converted into a `hana::set` with
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//! `to<set_tag>`. The elements of the structure must all be compile-time
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//! `Comparable`. If the structure contains duplicate elements, only
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//! the first occurence will appear in the resulting set. More
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//! specifically, conversion from a `Foldable` is equivalent to
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//! @code
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//! to<set_tag>(xs) == fold_left(xs, make_set(), insert)
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//! @endcode
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//!
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//! __Example__
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//! @include example/set/to.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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template <typename implementation_defined>
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struct set {
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//! Default-construct a set. This constructor only exists when all the
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//! elements of the set are default-constructible.
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constexpr set() = default;
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//! Copy-construct a set from another set. This constructor only
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//! exists when all the elements of the set are copy-constructible.
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constexpr set(set const& other) = default;
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//! Move-construct a set from another set. This constructor only
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//! exists when all the elements of the set are move-constructible.
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constexpr set(set&& other) = default;
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//! Equivalent to `hana::equal`
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template <typename X, typename Y>
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friend constexpr auto operator==(X&& x, Y&& y);
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//! Equivalent to `hana::not_equal`
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template <typename X, typename Y>
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friend constexpr auto operator!=(X&& x, Y&& y);
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//! Equivalent to `hana::at_key`
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template <typename Key>
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constexpr decltype(auto) operator[](Key&& key);
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};
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#else
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template <typename ...Xs>
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struct set;
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#endif
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//! Tag representing the `hana::set` container.
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//! @relates hana::set
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struct set_tag { };
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//! Function object for creating a `hana::set`.
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//! @relates hana::set
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//!
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//! Given zero or more values `xs...`, `make<set_tag>` returns a `set`
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//! containing those values. The values must all be compile-time
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//! `Comparable`, and no duplicate values may be provided. To create
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//! a `set` from a sequence with possible duplicates, use `to<set_tag>`
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//! instead.
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//!
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//!
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//! Example
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//! -------
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//! @include example/set/make.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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template <>
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constexpr auto make<set_tag> = [](auto&& ...xs) {
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return set<implementation_defined>{forwarded(xs)...};
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};
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#endif
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//! Equivalent to `make<set_tag>`; provided for convenience.
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//! @relates hana::set
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//!
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//!
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//! Example
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//! -------
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//! @include example/set/make.cpp
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constexpr auto make_set = make<set_tag>;
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//! Insert an element in a `hana::set`.
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//! @relates hana::set
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//!
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//! If the set already contains an element that compares equal, then
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//! nothing is done and the set is returned as is.
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//!
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//!
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//! @param set
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//! The set in which to insert a value.
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//!
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//! @param element
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//! The value to insert. It must be compile-time `Comparable`.
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//!
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//!
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//! Example
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//! -------
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//! @include example/set/insert.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto insert = [](auto&& set, auto&& element) {
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return tag-dispatched;
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};
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#endif
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//! Remove an element from a `hana::set`.
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//! @relates hana::set
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//!
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//! Returns a new set containing all the elements of the original,
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//! except the one comparing `equal` to the given element. If the set
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//! does not contain such an element, a new set equal to the original
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//! set is returned.
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//!
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//!
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//! @param set
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//! The set in which to remove a value.
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//!
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//! @param element
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//! The value to remove. It must be compile-time `Comparable`.
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//!
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//!
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//! Example
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//! -------
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//! @include example/set/erase_key.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto erase_key = [](auto&& set, auto&& element) {
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return tag-dispatched;
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};
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#endif
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//! Returns the union of two sets.
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//! @relates hana::set
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//!
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//! Given two sets `xs` and `ys`, `union_(xs, ys)` is a new set containing
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//! all the elements of `xs` and all the elements of `ys`, without
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//! duplicates. For any object `x`, the following holds: `x` is in
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//! `hana::union_(xs, ys)` if and only if `x` is in `xs` or `x` is in `ys`.
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//!
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//!
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//! @param xs, ys
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//! Two sets to compute the union of.
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//!
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//!
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//! Example
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//! -------
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//! @include example/set/union.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto union_ = [](auto&& xs, auto&& ys) {
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return tag-dispatched;
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};
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#endif
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//! Returns the intersection of two sets.
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//! @relates hana::set
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//!
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//! Given two sets `xs` and `ys`, `intersection(xs, ys)` is a new set
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//! containing exactly those elements that are present both in `xs` and
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//! in `ys`.
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//! In other words, the following holds for any object `x`:
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//! @code
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//! x ^in^ intersection(xs, ys) if and only if x ^in^ xs && x ^in^ ys
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//! @endcode
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//!
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//!
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//! @param xs, ys
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//! Two sets to intersect.
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//!
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//!
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//! Example
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//! -------
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//! @include example/set/intersection.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto intersection = [](auto&& xs, auto&& ys) {
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return tag-dispatched;
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};
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#endif
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//! Equivalent to `to<set_tag>`; provided for convenience.
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//! @relates hana::set
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constexpr auto to_set = to<set_tag>;
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//! Returns the set-theoretic difference of two sets.
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//! @relates hana::set
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//!
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//! Given two sets `xs` and `ys`, `difference(xs, ys)` is a new set
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//! containing all the elements of `xs` that are _not_ contained in `ys`.
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//! For any object `x`, the following holds:
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//! @code
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//! x ^in^ difference(xs, ys) if and only if x ^in^ xs && !(x ^in^ ys)
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//! @endcode
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//!
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//!
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//! This operation is not commutative, i.e. `difference(xs, ys)` is not
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//! necessarily the same as `difference(ys, xs)`. Indeed, consider the
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//! case where `xs` is empty and `ys` isn't. Then, `difference(xs, ys)`
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//! is empty but `difference(ys, xs)` is equal to `ys`. For the symmetric
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//! version of this operation, see `symmetric_difference`.
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//!
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//!
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//! @param xs
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//! A set param to remove values from.
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//!
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//! @param ys
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//! The set whose values are removed from `xs`.
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//!
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//!
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//! Example
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//! -------
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//! @include example/set/difference.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto difference = [](auto&& xs, auto&& ys) {
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return tag-dispatched;
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};
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#endif
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//! Returns the symmetric set-theoretic difference of two sets.
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//! @relates hana::set
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//!
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//! Given two sets `xs` and `ys`, `symmetric_difference(xs, ys)` is a new
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//! set containing all the elements of `xs` that are not contained in `ys`,
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//! and all the elements of `ys` that are not contained in `xs`. The
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//! symmetric difference of two sets satisfies the following:
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//! @code
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//! symmetric_difference(xs, ys) == union_(difference(xs, ys), difference(ys, xs))
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//! @endcode
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//!
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//!
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//! @param xs, ys
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//! Two sets to compute the symmetric difference of.
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//!
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//!
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//! Example
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//! -------
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//! @include example/set/symmetric_difference.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto symmetric_difference = [](auto&& xs, auto&& ys) {
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return tag-dispatched;
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};
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#endif
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_FWD_SET_HPP
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