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std::unorde...imap::erase(3)   C++ Standard Libary  std::unorde...imap::erase(3)

NAME
     std::unordered_multimap::erase - std::unordered_multimap::erase

Synopsis
	iterator  erase( iterator pos );			      (1) (since
     C++11)
	iterator erase( const_iterator pos );			     (2)  (since
     C++11)
	iterator  erase( const_iterator first, const_iterator last ); (3) (since
     C++11)
	size_type erase( const Key& key );			     (4)  (since
     C++11)
	template<  class K >					      (5) (since
     C++23)
	size_type erase( K&& x );

	Removes specified elements from the container. The order of the  remain-
     ing elements
	is preserved. (This makes it possible to erase individual elements while
     iterating
	through the container.)

	1,2) Removes the element at pos.
	3)  Removes  the  elements  in	the range [first, last), which must be a
     valid range in
	*this.
	4) Removes all elements with the key equivalent to key.
	5) Removes all elements with key that compares equivalent to  the  value
     x. This
	overload  participates in overload resolution only if Hash::is_transpar-
     ent and
	KeyEqual::is_transparent are valid and each denotes a type, and  neither
     iterator nor
	const_iterator	is implicitly convertible from K. This assumes that such
     Hash is
	callable with both K and Key type, and that the KeyEqual is transparent,
     which,
	together, allows calling this function without constructing an	instance
     of Key.

	References  and  iterators to the erased elements are invalidated. Other
     iterators and
	references are not invalidated.

	The iterator pos must be valid and dereferenceable. Thus the end() iter-
     ator (which
	is valid, but is not dereferenceable) cannot be used as a value for pos.

Parameters
	pos	    - iterator to the element to remove
	first, last - range of elements to remove
	key	    - key value of the elements to remove
	x	    - a value of any type that	can  be  transparently	compared
     with a key
		      denoting the elements to remove

Return value
	1-3) Iterator following the last removed element.
	4) Number of elements removed.
	5) Number of elements removed.

Exceptions
	1-3) Throws nothing.
	4,5) Any exceptions thrown by the Hash and KeyEqual object.

Complexity
	Given an instance c of unordered_multimap:

	1,2) Average case: constant, worst case: c.size().
	3) Average case: std::distance(first, last), worst case: c.size().
	4) Average case: c.count(key), worst case: c.size().
	5) Average case: c.count(x), worst case: c.size().

Notes
		    Feature-test macro		     Value    Std	    Fea-
     ture
								    Heteroge-
     neous erasure in
								    associative
     containers
	__cpp_lib_associative_heterogeneous_erasure   202110L  (C++23)	and  un-
     ordered
								    associative
     containers;
								    overload (5)

Example
     // Run this code

      #include <unordered_map>
      #include <iostream>

      int main()
      {
	  std::unordered_multimap<int, std::string> c =
	  {
	      {1, "one"}, {2, "two"}, {3, "three"},
	      {4, "four"}, {5, "five"}, {6, "six"}
	  };

	  // erase all odd numbers from c
	  for (auto it = c.begin(); it != c.end();)
	  {
	      if (it->first % 2 != 0)
		  it = c.erase(it);
	      else
		  ++it;
	  }

	  for (auto& p : c)
	      std::cout << p.second << ' ';
	  std::cout << '\n';
      }

Possible output:
      two four six

       Defect reports

	The following behavior-changing defect	reports  were  applied	retroac-
     tively to
	previously published C++ standards.

	   DR	  Applied to	      Behavior as published		 Correct
     behavior
	LWG 2059 C++11	    there was ambiguity for overload (2)    added  over-
     load (1)
			    the order of non-equivalent elements
	LWG  2356 C++11      that are				     required to
     be preserved
			    not erased was not guaranteed to be
			    preserved

See also
	clear clears the contents
	      (public member function)

http://cppreference.com 	   2024.06.10	    std::unorde...imap::erase(3)
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