hash_map::const_reference

A type that provides a reference to a const element stored in a hash_map for reading and performing const operations.

typedef list<typename _Traits::value_type, typename _Traits::allocator_type>::const_reference const_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_const_ref.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 because the 
   // non-const_reference cannot be used to access the key
   // int &Ref1 = ( hm1.begin( ) -> first );

   cout << "The key of the 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 the first element in the hash_map is "
        << Ref2 << "." << endl;
}

The key of the first element in the hash_map is 1.
The data value of the first element in the hash_map is 10.

Requirements

Header: <hash_map>

Namespace: stdext

See Also

Concepts

hash_map Class

hash_map Members

Standard Template Library