unordered_map::difference_type
The type of a signed distance between two elements.
typedef T3 difference_type;
Remarks
The signed integer type describes an object that can represent the difference between the addresses of any two elements in the controlled sequence. It is described here as a synonym for the implementation-defined type T3.
Example
// std_tr1__unordered_map__unordered_map_difference_type.cpp
// compile with: /EHsc
#include <unordered_map>
#include <iostream>
typedef std::unordered_map<char, int> Mymap;
int main()
{
Mymap c1;
c1.insert(Mymap::value_type('a', 1));
c1.insert(Mymap::value_type('b', 2));
c1.insert(Mymap::value_type('c', 3));
// display contents " [c 3] [b 2] [a 1]"
for (Mymap::const_iterator it = c1.begin();
it != c1.end(); ++it)
std::cout << " [" << it->first << ", " << it->second << "]";
std::cout << std::endl;
// compute positive difference
Mymap::difference_type diff = 0;
for (Mymap::const_iterator it = c1.begin();
it != c1.end(); ++it)
++diff;
std::cout << "end()-begin() == " << diff << std::endl;
// compute negative difference
diff = 0;
for (Mymap::const_iterator it = c1.end();
it != c1.begin(); --it)
--diff;
std::cout << "begin()-end() == " << diff << std::endl;
return (0);
}
[c, 3] [b, 2] [a, 1] end()-begin() == 3 begin()-end() == -3
Requirements
Header: <unordered_map>
Namespace: std