vector::front
Returns a reference to the first element in a vector.
reference front( );
const_reference front( ) const;
Return Value
A reference to the first element in the vector object. If the vector is empty, the return is undefined.
Remarks
If the return value of front is assigned to a const_reference, the vector object cannot be modified. If the return value of front is assigned to a reference, the vector object can be modified.
When compiling with _SECURE_SCL 1, a runtime error will occur if you attempt to access an element in an empty vector. See Checked Iterators for more information.
Example
// vector_front.cpp
// compile with: /EHsc
#include <vector>
#include <iostream>
int main( )
{
using namespace std;
vector <int> v1;
v1.push_back( 10 );
v1.push_back( 11 );
int& i = v1.front( );
const int& ii = v1.front( );
cout << "The first integer of v1 is "<< i << endl;
// by incrementing i, we move the the front reference to the second element
i++;
cout << "Now, the first integer of v1 is "<< i << endl;
}
Output
The first integer of v1 is 10
Now, the first integer of v1 is 11
Requirements
Header: <vector>
Namespace: std