hash_set::insert

Inserts an element or a range of elements into a hash_set.

pair<iterator, bool> insert(
   const value_type& _Val
);
iterator insert(
   iterator _Where,
   const value_type& _Val
);
template<class InputIterator>
   void insert(
      InputIterator _First,
      InputIterator _Last
   );

Parameters

• _Val
  The value of an element to be inserted into the hash_set unless the hash_set already contains that element or, more generally, an element whose key is equivalently ordered.

• _Where
  The place to start searching for the correct point of insertion. (Insertion can occur in amortized constant time, instead of logarithmic time, if the insertion point immediately follows _Where.)

• _First
  The position of the first element to be copied from a hash_set.

• _Last
  The position just beyond the last element to be copied from a hash_set.

Return Value

The first insert member function returns a pair whose bool component returns true if an insertion was make and false if the hash_set already contained an element whose key had an equivalent value in the ordering, and whose iterator component returns the address where a new element was inserted or where the element was already located.

To access the iterator component of a pair pr returned by this member function, use pr.first and to dereference it, use *(pr.first). To access the bool component of a pair pr returned by this member function, use pr.second, and to dereference it, use *(pr.second).

The second insert member function returns an iterator that points to the position where the new element was inserted into the hash_set.

Remarks

The third member function inserts the sequence of element values into a hash_set corresponding to each element addressed by an iterator of in the range [_First, _Last) of a specified hash_set.

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_set_insert.cpp
// compile with: /EHsc
#include <hash_set>
#include <iostream>

int main( )
{
   using namespace std;
   using namespace stdext;
   hash_set <int>::iterator hs1_pIter, hs2_pIter;

   hash_set <int, hash_compare <int, less<int> > > hs1, hs2;
   hs1.insert( 10 );
   hs1.insert( 20 );
   hs1.insert( 30 );
   hs1.insert( 40 );

   cout << "The original hs1 =";
   for ( hs1_pIter = hs1.begin( ); hs1_pIter != hs1.end( );
         hs1_pIter++ )
      cout << " " << *hs1_pIter;
   cout << "." << endl;

   pair< hash_set<int>::iterator, bool > pr;
   pr = hs1.insert( 10 );

   if(pr.second == true)
   {
      cout << "The element 10 was inserted in hs1 successfully."
           << endl;
   }
   else
   {
      cout << "The element 10 already exists in hs1 and"
           << " *( pr.first ) = " << *( pr.first ) << "."
           << endl;
   }

   hs1.insert( --hs1.end( ), 50 );

   cout << "After the insertions, hs1 =";
   for ( hs1_pIter = hs1.begin( ); hs1_pIter != hs1.end( );
         hs1_pIter++ )
      cout << " " << *hs1_pIter;
   cout << "." << endl;

   hs2.insert( 100 );
   hs2.insert( ++hs1.begin( ), --hs1.end( ) );

   cout << "hs2 =";
   for ( hs2_pIter = hs2.begin( ); hs2_pIter != hs2.end( );
         hs2_pIter++ )
      cout << " " << *hs2_pIter;
   cout << "." << endl;
}

The original hs1 = 40 10 20 30.
The element 10 already exists in hs1 and *( pr.first ) = 10.
After the insertions, hs1 = 40 10 50 20 30.
hs2 = 10 50 20 100.

Requirements

Header: <hash_set>

Namespace: stdext

See Also

Concepts

hash_set Class

hash_set Members

Standard Template Library