#include<compare>// see [compare.syn]#include<initializer_list>// see [initializer.list.syn]namespace std {// [unord.set], class template unordered_settemplate<class Key,
class Hash = hash<Key>,
class Pred = equal_to<Key>,
class Alloc = allocator<Key>>class unordered_set;
// [unord.multiset], class template unordered_multisettemplate<class Key,
class Hash = hash<Key>,
class Pred = equal_to<Key>,
class Alloc = allocator<Key>>class unordered_multiset;
template<class Key, class Hash, class Pred, class Alloc>booloperator==(const unordered_set<Key, Hash, Pred, Alloc>& a,
const unordered_set<Key, Hash, Pred, Alloc>& b);
template<class Key, class Hash, class Pred, class Alloc>booloperator==(const unordered_multiset<Key, Hash, Pred, Alloc>& a,
const unordered_multiset<Key, Hash, Pred, Alloc>& b);
template<class Key, class Hash, class Pred, class Alloc>void swap(unordered_set<Key, Hash, Pred, Alloc>& x,
unordered_set<Key, Hash, Pred, Alloc>& y)noexcept(noexcept(x.swap(y)));
template<class Key, class Hash, class Pred, class Alloc>void swap(unordered_multiset<Key, Hash, Pred, Alloc>& x,
unordered_multiset<Key, Hash, Pred, Alloc>& y)noexcept(noexcept(x.swap(y)));
template<class K, class H, class P, class A, class Predicate>typename unordered_set<K, H, P, A>::size_type
erase_if(unordered_set<K, H, P, A>& c, Predicate pred);
template<class K, class H, class P, class A, class Predicate>typename unordered_multiset<K, H, P, A>::size_type
erase_if(unordered_multiset<K, H, P, A>& c, Predicate pred);
namespace pmr {template<class Key,
class Hash = hash<Key>,
class Pred = equal_to<Key>>using unordered_set = std::unordered_set<Key, Hash, Pred,
polymorphic_allocator<Key>>;
template<class Key,
class Hash = hash<Key>,
class Pred = equal_to<Key>>using unordered_multiset = std::unordered_multiset<Key, Hash, Pred,
polymorphic_allocator<Key>>;
}}