vector::front

Returns a reference to the first element in a vector.

reference front( ); 
const_reference front( ) const;

A reference to the first element in the vector object. If the vector is empty, the return is undefined.

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.

// 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;
}

The first integer of v1 is 10
Now, the first integer of v1 is 11

Header: <vector>

Namespace: std

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