hash_set::difference_type
A signed integer type that can be used to represent the number of elements of a hash_set in a range between elements pointed to by iterators.
typedef list<typename Traits::value_type, typename Traits::allocator_type>::difference_type difference_type;
Remarks
The difference_type is the type returned when subtracting or incrementing through iterators of the container. The difference_type is typically used to represent the number of elements in the range [_First, _Last) between the iterators _First and _Last, includes the element pointed to by _First and the range of elements up to, but not including, the element pointed to by _Last.
Note that although difference_type is available for all iterators that satisfy the requirements of an input iterator, which includes the class of bidirectional iterators supported by reversible containers such as set, subtraction between iterators is only supported by random-access iterators provided by a random access container, such as vector or deque.
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_diff_type.cpp
// compile with: /EHsc
#define _DEFINE_DEPRECATED_HASH_CLASSES 0
#include <iostream>
#include <hash_set>
#include <algorithm>
int main( )
{
using namespace std;
using namespace stdext;
hash_set <int> hs1;
hash_set <int>::iterator hs1_Iter, hs1_bIter, hs1_eIter;
hs1.insert( 20 );
hs1.insert( 10 );
hs1.insert( 20 ); // Won't insert as hash_set elements are unique
hs1_bIter = hs1.begin( );
hs1_eIter = hs1.end( );
hash_set <int>::difference_type df_typ5, df_typ10, df_typ20;
df_typ5 = count( hs1_bIter, hs1_eIter, 5 );
df_typ10 = count( hs1_bIter, hs1_eIter, 10 );
df_typ20 = count( hs1_bIter, hs1_eIter, 20 );
// The keys, and hence the elements, of a hash_set are unique,
// so there is at most one of a given value
cout << "The number '5' occurs " << df_typ5
<< " times in hash_set hs1.\n";
cout << "The number '10' occurs " << df_typ10
<< " times in hash_set hs1.\n";
cout << "The number '20' occurs " << df_typ20
<< " times in hash_set hs1.\n";
// Count the number of elements in a hash_set
hash_set <int>::difference_type df_count = 0;
hs1_Iter = hs1.begin( );
while ( hs1_Iter != hs1_eIter)
{
df_count++;
hs1_Iter++;
}
cout << "The number of elements in the hash_set hs1 is: "
<< df_count << "." << endl;
}
The number '5' occurs 0 times in hash_set hs1.
The number '10' occurs 1 times in hash_set hs1.
The number '20' occurs 1 times in hash_set hs1.
The number of elements in the hash_set hs1 is: 2.
Requirements
Header: <hash_set>
Namespace: stdext