Constructs a map that is empty or that is a copy of all or part of some other map.
map( );
explicit map(
const Traits& _Comp
);
map(
const Traits& _Comp,
const Allocator& _Al
);
map(
const map<Key, Type, Traits, Allocator>& _Right
);
template<class InputIterator>
map(
InputIterator _First,
InputIterator _Last
);
template<class InputIterator>
map(
InputIterator _First,
InputIterator _Last,
const Traits& _Comp
);
template<class InputIterator>
map(
InputIterator _First,
InputIterator _Last,
const Traits& _Comp,
const Allocator& _Al
);
Parameters
_Al The storage allocator class to be used for this map object, which defaults to Allocator.
_Comp The comparison function of type constTraits used to order the elements in the map, which defaults to hash_compare.
_Right The map of which the constructed 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 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 map.
All constructors store a function object of type Traits that is used to establish an order among the keys of the map and that can later be returned by calling key_comp.
The first three constructors specify an empty initial map, 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 map _Right.
The last three constructors copy the range [_First, _Last) of a map with increasing explicitness in specifying the type of comparison function of class Traits and allocator.
Example
// map_map.cpp
// compile with: /EHsc
#include <map>
#include <iostream>
int main( )
{
using namespace std;
typedef pair <int, int> Int_Pair;
map <int, int>::iterator m1_Iter, m3_Iter, m4_Iter, m5_Iter, m6_Iter;
map <int, int, greater<int> >::iterator m2_Iter;
// Create an empty map m0 of key type integer
map <int, int> m0;
// Create an empty map m1 with the key comparison
// function of less than, then insert 4 elements
map <int, int, less<int> > m1;
m1.insert( Int_Pair( 1, 10 ) );
m1.insert( Int_Pair( 2, 20 ) );
m1.insert( Int_Pair( 3, 30 ) );
m1.insert( Int_Pair( 4, 40 ) );
// Create an empty map m2 with the key comparison
// function of geater than, then insert 2 elements
map <int, int, greater<int> > m2;
m2.insert( Int_Pair( 1, 10 ) );
m2.insert( Int_Pair( 2, 20 ) );
// Create a map m3 with the
// allocator of map m1
map <int, int>::allocator_type m1_Alloc;
m1_Alloc = m1.get_allocator( );
map <int, int> m3( less<int>( ), m1_Alloc );
m3.insert( Int_Pair( 3, 30 ) );
// Create a copy, map m4, of map m1
map <int, int> m4( m1 );
// Create a map m5 by copying the range m1[_First, _Last)
map <int, int>::const_iterator m1_bcIter, m1_ecIter;
m1_bcIter = m1.begin( );
m1_ecIter = m1.begin( );
m1_ecIter++;
m1_ecIter++;
map <int, int> m5(m1_bcIter, m1_ecIter);
// Create a map m6 by copying the range m4[_First, _Last)
// and with the allocator of map m2
map <int, int>::allocator_type m2_Alloc;
m2_Alloc = m2.get_allocator( );
map <int, int> m6( m4.begin( ), ++m4.begin( ), less<int>( ), m2_Alloc);
cout << "m1 =";
for ( m1_Iter = m1.begin( ); m1_Iter != m1.end( ); m1_Iter++ )
cout << " " << m1_Iter -> second;
cout << endl;
cout << "m2 =";
for ( m2_Iter = m2.begin( ); m2_Iter != m2.end( ); m2_Iter++ )
cout << " " << m2_Iter -> second;
cout << endl;
cout << "m3 =";
for ( m3_Iter = m3.begin( ); m3_Iter != m3.end( ); m3_Iter++ )
cout << " " << m3_Iter -> second;
cout << endl;
cout << "m4 =";
for ( m4_Iter = m4.begin( ); m4_Iter != m4.end( ); m4_Iter++ )
cout << " " << m4_Iter -> second;
cout << endl;
cout << "m5 =";
for ( m5_Iter = m5.begin( ); m5_Iter != m5.end( ); m5_Iter++ )
cout << " " << m5_Iter -> second;
cout << endl;
cout << "m6 =";
for ( m6_Iter = m6.begin( ); m6_Iter != m6.end( ); m6_Iter++ )
cout << " " << m6_Iter -> second;
cout << endl;
}
out put
m1 = 10 20 30 40m2 = 20 10m3 = 30m4 = 10 20 30 40m5 = 10 20m6 = 10
Header: <map>
Namespace: std
