hash_map::hash_map
Constructs a hash_map that is empty or that is a copy of all or part of some other hash_map.
hash_map( );
explicit hash_map(
const Traits& _Comp
);
hash_map(
const Traits& _Comp,
const Allocator& _Al
);
hash_map(
const hash_map& _Right
);
template<class InputIterator>
hash_map(
InputIterator _First,
InputIterator _Last
);
template<class InputIterator>
hash_map(
InputIterator _First,
InputIterator _Last,
const Traits& _Comp
);
template<class InputIterator>
hash_map(
InputIterator _First,
InputIterator _Last,
const Traits& _Comp,
const Allocator& _Al
);
Parameters
_Al
The storage allocator class to be used for this hash_map object, which defaults to Allocator._Comp
The comparison function of type constTraits used to order the elements in the hash_map, which defaults to hash_compare._Right
The hash_map of which the constructed map 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_map 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_map.
All constructors store a function object of type Traits that is used to establish an order among the keys of the hash_map and that can later be returned by calling key_comp.
The first three constructors specify an empty initial hash_map, the second, in addition, 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 keyword explicit suppresses certain kinds of automatic type conversion.
The fourth constructor specifies a copy of the hash_map _Right.
The last three constructors copy the range [_First, _Last) of a hash_map with increasing explicitness in specifying the type of comparison function of class Traits and allocator.
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_hash_map.cpp
// compile with: /EHsc
#include <ostream>
#include <hash_map>
#include <iostream>
#include <fstream>
#include <string.h>
using namespace std;
typedef char * MyStr;
struct MyInt
{
int i;
friend ostream& operator<<(ostream& ii, MyInt& jj);
MyInt(int j = 0) {
i = j;
}
};
struct greater_str
{
bool operator()(const MyStr & x, const MyStr & y) const {
if (strcmp(x, y) < 0)
return true;
return false;
}
};
struct less_str {
bool operator()(const MyStr & x, const MyStr & y) const
{
if (strcmp(x, y) > 0)
return true;
return false;
}
};
ostream& operator<<(ostream& o, MyInt& j) {
o << j.i;
return o;
}
int main()
{
using namespace stdext;
typedef pair <MyStr, MyInt> Int_Pair;
hash_map<MyStr, MyInt>::iterator hm1_Iter, hm3_Iter, hm4_Iter, hm5_Iter, hm6_Iter;
hash_map<MyStr, MyInt, hash_compare<MyStr, greater_str> >::iterator hm2_Iter;
// Create an empty hash_map hm0 of key type integer
hash_map<MyStr, MyInt> hm0;
// Create an empty hash_map hm1 with the key comparison
// function of less than, then insert 4 elements
hash_map<MyStr, MyInt, hash_compare<MyStr, less_str> > hm1;
hm1.insert(Int_Pair("one", 0));
hm1.insert(Int_Pair("two", 10));
hm1.insert(Int_Pair("three", 20));
hm1.insert(Int_Pair("four", 30));
hm1.insert(Int_Pair("five", 40));
// Create an empty hash_map hm2 with the key comparison
// function of geater than, then insert 2 elements
hash_map<MyStr, MyInt, hash_compare<MyStr, greater_str> > hm2;
hm2.insert(Int_Pair("one", 10));
hm2.insert(Int_Pair("two", 20));
// Create a hash_map hm3 with the
// allocator of hash_map hm1
hash_map<MyStr, MyInt>::allocator_type hm1_Alloc;
hm1_Alloc = hm1.get_allocator();
hash_map<MyStr, MyInt, hash_compare<MyStr, less_str> > hm3(hash_compare<MyStr, less_str > (), hm1_Alloc);
hm3.insert(Int_Pair("three", 30));
// Create a copy, hash_map hm4, of hash_map hm1
hash_map<MyStr, MyInt, hash_compare<MyStr, less_str> > hm4(hm1);
// Create a hash_map hm5 by copying the range hm1[_First, _Last)
hash_map<MyStr, MyInt>::const_iterator hm1_bcIter, hm1_ecIter;
hm1_bcIter = hm1.begin();
hm1_ecIter = hm1.begin();
hm1_ecIter++;
hm1_ecIter++;
hash_map<MyStr, MyInt> hm5(hm1_bcIter, hm1_ecIter);
// Create a hash_map hm6 by copying the range hm4[_First, _Last)
// and with the allocator of hash_map hm2
hash_map<MyStr, MyInt>::allocator_type hm2_Alloc;
hm2_Alloc = hm2.get_allocator();
hash_map<MyStr, MyInt, hash_compare<MyStr, less_str> > hm6(hm4.begin(), ++hm4.begin(), hash_compare<MyStr, less_str > (), hm2_Alloc);
cout << "hm1 =";
for (hm1_Iter = hm1.begin(); hm1_Iter != hm1.end(); hm1_Iter+)
cout << " " << hm1_Iter -> second;
cout << endl;
cout << "hm2 =";
for (hm2_Iter = hm2.begin(); hm2_Iter != hm2.end(); hm2_Iter+)
cout << " " << hm2_Iter -> second;
cout << endl;
cout << "hm3 =";
for (hm3_Iter = hm3.begin(); hm3_Iter != hm3.end(); hm3_Iter+)
cout << " " << hm3_Iter -> second;
cout << endl;
cout << "hm4 =";
for (hm4_Iter = hm4.begin(); hm4_Iter != hm4.end(); hm4_Iter+)
cout << " " << hm4_Iter -> second;
cout << endl;
cout << "hm5 =";
for (hm5_Iter = hm5.begin(); hm5_Iter != hm5.end(); hm5_Iter+)
cout << " " << hm5_Iter -> second;
cout << endl;
cout << "hm6 =";
for (hm6_Iter = hm6.begin(); hm6_Iter != hm6.end(); hm6_Iter+)
cout << " " << hm6_Iter -> second;
cout << endl;
}
Sample Output
hm1 = 20 0 30 40 10
hm2 = 10 20
hm3 = 30
hm4 = 20 0 30 40 10
hm5 = 0 20
hm6 = 20
Requirements
Header: <hash_map>
Namespace: stdext