hash_map::reference
A type that provides a reference to an element stored in a hash_map.
typedef list<typename _Traits::value_type, typename _Traits::allocator_type>::reference reference;
Remarks
In Visual C++ .NET 2003, members of the <hash_map> and <hash_set> header files are no longer in the std namespace, but rather have been moved into the stdext namespace. See The stdext Namespace for more information.
Example
// hash_map_reference.cpp
// compile with: /EHsc
#define _DEFINE_DEPRECATED_HASH_CLASSES 0
#include <hash_map>
#include <iostream>
int main( )
{
using namespace std;
using namespace stdext;
hash_map <int, int> hm1;
typedef pair <int, int> Int_Pair;
hm1.insert ( Int_Pair ( 1, 10 ) );
hm1.insert ( Int_Pair ( 2, 20 ) );
// Declare and initialize a const_reference &Ref1
// to the key of the first element
const int &Ref1 = ( hm1.begin( ) -> first );
// The following line would cause an error as the
// non-const_reference cannot be used to access the key
// int &Ref1 = ( hm1.begin( ) -> first );
cout << "The key of first element in the hash_map is "
<< Ref1 << "." << endl;
// Declare and initialize a reference &Ref2
// to the data value of the first element
int &Ref2 = ( hm1.begin( ) -> second );
cout << "The data value of first element in the hash_map is "
<< Ref2 << "." << endl;
// The non-const_reference can be used to modify the
// data value of the first element
Ref2 = Ref2 + 5;
cout << "The modified data value of first element is "
<< Ref2 << "." << endl;
}
The key of first element in the hash_map is 1. The data value of first element in the hash_map is 10. The modified data value of first element is 15.
Requirements
Header: <hash_map>
Namespace: stdext