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std::unordered_map::at(3)     C++ Standard Libary    std::unordered_map::at(3)

NAME
       std::unordered_map::at -	std::unordered_map::at

Synopsis
	  T& at( const Key& key	);	       (1) (since C++11)
	  const	T& at( const Key& key )	const; (2) (since C++11)
	  template< class K >		       (3) (since C++26)
	  T& at( const K& x );
	  template< class K >		       (4) (since C++26)
	  const	T& at( const K&	x ) const;

	  Returns  a  reference	to the mapped value of the element with	speci-
       fied key. If no
	  such element exists,	an  exception  of  type	 std::out_of_range  is
       thrown.

	  1,2) The key is equivalent to	key.
	  3,4)	The  key  compares equivalent to the value x. The reference to
       the mapped value
	  is obtained as if by expression this->find(x)->second.
	  The expression this->find(x) must be well-formed and	have  well-de-
       fined behavior,
	  otherwise the	behavior is undefined.
	  These	  overloads   participate   in	overload  resolution  only  if
       Hash::is_transparent and
	  KeyEqual::is_transparent are valid and each denotes a	type. This as-
       sumes 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.

Parameters
	  key -	the key	of the element to find
	  x   -	a value	of any type that can be	transparently compared with  a
       key

Return value
	  A reference to the mapped value of the requested element.

Exceptions
	  1,2)	std::out_of_range  if  the  container does not have an element
       with the	specified
	  key.
	  3,4) std::out_of_range if the	container does not have	the  specified
       element,	that
	  is, if find(x) == end() is true.

Complexity
	  Average case:	constant, worst	case: linear in	size.

Notes
		       Feature-test    macro		       Value	   Std
       Feature
									Het-
       erogeneous
									over-
       loads for the
									re-
       maining member
	  __cpp_lib_associative_heterogeneous_insertion	202311L	(C++26)	 func-
       tions in	ordered
									and
       unordered
									asso-
       ciative
									con-
       tainers.	(3,4)

Example
	   This	section	is incomplete
	   Reason: no example

See also
	  operator[] access or insert specified	element
		     (public member function)

Category:
	    * Todo no example

http://cppreference.com		  2024.06.10	     std::unordered_map::at(3)

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