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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 specified
     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-defined
     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 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.

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 ele-
     ment, that
	is, if find(x) == end() is true.

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

Notes
		     Feature-test     macro		       Value	     Std
     Feature
								      Heteroge-
     neous
								      overloads
     for the
								      remaining
     member
	__cpp_lib_associative_heterogeneous_insertion  202311L (C++26) functions
     in ordered
								      and    un-
     ordered
								      associa-
     tive
								      contain-
     ers. (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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