hash_set::hash_set
Constructs a hash_set that is empty or that is a copy of all or part of some other hash_set.
hash_set( );
explicit hash_set(
const Traits& _Comp
);
hash_set(
const Traits& _Comp,
const Allocator& _Al
);
hash_set(
const hash_set<Key, Traits, Allocator>& _Right
);
template<class InputIterator>
hash_set(
InputIterator _First,
InputIterator _Last
);
template<class InputIterator>
hash_set(
InputIterator _First,
InputIterator _Last,
const Traits& _Comp
);
template<class InputIterator>
hash_set(
InputIterator _First,
InputIterator _Last,
const Traits& _Comp,
const Allocator& _Al
);
Parameters
_Al
The storage allocator class to be used for this hash_set object, which defaults to Allocator._Comp
The comparison function of type constTraits used to order the elements in the hash_set, which defaults to hash_compare._Right
The hash_set of which the constructed hash_set is to be a copy._First
The position of the first element in the range of elements to be copied._Last
The position of the first element beyond the range of elements to be copied.
Remarks
All constructors store a type of allocator object that manages memory storage for the hash_set and that can later be returned by calling get_allocator. The allocator parameter is often omitted in the class declarations and preprocessing macros used to substitute alternative allocators.
All constructors initialize their hash_sets.
All constructors store a function object of type Traits that is used to establish an order among the keys of the hash_set and that can later be returned by calling key_comp. For more information on Traits see the hash_set Class topic.
The first three constructors specify an empty initial hash_set, the second specifying the type of comparison function (_Comp) to be used in establishing the order of the elements and the third explicitly specifying the allocator type (_Al) to be used. The key word explicit suppresses certain kinds of automatic type conversion.
The fourth constructor specifies a copy of the hash_set _Right.
The last three constructors copy the range [_First, _Last) of a hash_set with increasing explicitness in specifying the type of comparison function of class Traits and allocator.
The actual order of elements in a hash_set container depends on the hash function, the ordering function and the current size of the hash table and cannot, in general, be predicted as it could with the set container, where it was determined by the ordering function alone.
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_hash_set.cpp
// compile with: /EHsc
#include <hash_set>
#include <iostream>
int main( )
{
using namespace std;
using namespace stdext;
hash_set <int>::iterator hs1_Iter, hs3_Iter, hs4_Iter,
hs5_Iter, hs6_Iter;
hash_set <int, hash_compare <int, greater<int> > >::iterator
hs2_Iter;
// Create an empty hash_set hs0 of key type integer
hash_set <int> hs0;
// Create an empty hash_set hs1 with the key comparison
// function of less than, then insert 4 elements
hash_set <int, hash_compare <int, less<int> > > hs1;
hs1.insert( 10 );
hs1.insert( 20 );
hs1.insert( 30 );
hs1.insert( 40 );
// Create an empty hash_set hs2 with the key comparison
// function of geater than, then insert 2 elements
hash_set <int, hash_compare <int, greater<int> > > hs2;
hs2.insert(10);
hs2.insert(20);
// Create a hash_set hs3 with the
// allocator of hash_set hs1
hash_set <int>::allocator_type hs1_Alloc;
hs1_Alloc = hs1.get_allocator( );
hash_set <int> hs3( hash_compare <int, less<int> >( ),
hs1_Alloc );
hs3.insert( 30 );
// Create a copy, hash_set hs4, of hash_set hs1
hash_set <int> hs4( hs1 );
// Create a hash_set hs5 by copying the range hs1[_First, _Last)
hash_set <int>::const_iterator hs1_bcIter, hs1_ecIter;
hs1_bcIter = hs1.begin( );
hs1_ecIter = hs1.begin( );
hs1_ecIter++;
hs1_ecIter++;
hash_set <int> hs5( hs1_bcIter, hs1_ecIter );
// Create a hash_set hs6 by copying the range hs4[_First, _Last)
// and with the allocator of hash_set hs2
hash_set <int>::allocator_type hs2_Alloc;
hs2_Alloc = hs2.get_allocator( );
hash_set <int> hs6( hs4.begin( ), ++hs4.begin( ),
less<int>( ), hs2_Alloc );
cout << "hs1 = ";
for ( hs1_Iter = hs1.begin( ); hs1_Iter != hs1.end( );
hs1_Iter++ )
cout << *hs1_Iter << " ";
cout << endl;
cout << "hs2 = " ;
for ( hs2_Iter = hs2.begin( ); hs2_Iter != hs2.end( );
hs2_Iter++ )
cout << *hs2_Iter << " ";
cout << endl;
cout << "hs3 = ";
for ( hs3_Iter = hs3.begin( ); hs3_Iter != hs3.end( );
hs3_Iter++ )
cout << *hs3_Iter << " ";
cout << endl;
cout << "hs4 = ";
for ( hs4_Iter = hs4.begin( ); hs4_Iter != hs4.end( );
hs4_Iter++ )
cout << *hs4_Iter << " ";
cout << endl;
cout << "hs5 = ";
for ( hs5_Iter = hs5.begin( ); hs5_Iter != hs5.end( );
hs5_Iter++ )
cout << *hs5_Iter << " ";
cout << endl;
cout << "hs6 = ";
for ( hs6_Iter = hs6.begin( ); hs6_Iter != hs6.end( );
hs6_Iter++ )
cout << *hs6_Iter << " ";
cout << endl;
}
Output
hs1 = 40 10 20 30
hs2 = 10 20
hs3 = 30
hs4 = 40 10 20 30
hs5 = 40 10
hs6 = 40
Requirements
Header: <hash_set>
Namespace: stdext