map::begin
Returns an iterator addressing the first element in the map.
const_iterator begin( ) const;
iterator begin( );
Return Value
A bidirectional iterator addressing the first element in the map or the location succeeding an empty map.
Remark
If the return value of begin is assigned to a const_iterator, the elements in the map object cannot be modified. If the return value of begin is assigned to an iterator, the elements in the map object can be modified.
Example
// map_begin.cpp
// compile with: /EHsc
#include <map>
#include <iostream>
int main( )
{
using namespace std;
map <int, int> m1;
map <int, int> :: iterator m1_Iter;
map <int, int> :: const_iterator m1_cIter;
typedef pair <int, int> Int_Pair;
m1.insert ( Int_Pair ( 0, 0 ) );
m1.insert ( Int_Pair ( 1, 1 ) );
m1.insert ( Int_Pair ( 2, 4 ) );
m1_cIter = m1.begin ( );
cout << "The first element of m1 is " << m1_cIter -> first << endl;
m1_Iter = m1.begin ( );
m1.erase ( m1_Iter );
// The following 2 lines would err because the iterator is const
// m1_cIter = m1.begin ( );
// m1.erase ( m1_cIter );
m1_cIter = m1.begin( );
cout << "The first element of m1 is now " << m1_cIter -> first << endl;
}
The first element of m1 is 0 The first element of m1 is now 1
Requirements
Header: <map>
Namespace: std