Exchange the value, hasher, key-equality functor, and max_load_factor 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 both the (template parameter) types HASH and EQUAL provide no-throw swap operations; if an exception is thrown, both objects are left in valid but unspecified states. This operation guarantees O[1] complexity. The behavior is undefined unless either a was created with the same allocator as b or ALLOCATOR has the propagate_on_container_swap trait.
Declared in <bslstl_unorderedmultimap.h>
template<
class KEY,
class VALUE,
class HASH,
class EQUAL,
class ALLOCATOR>
void
swap(
unordered_multimap<KEY, VALUE, HASH, EQUAL, ALLOCATOR>& a,
unordered_multimap<KEY, VALUE, HASH, EQUAL, ALLOCATOR>& b) noexcept(false);