#include <boost/bit_logic/bit_vector.hpp> 
   void push_back ( bool val ) ;

The push_back() function adds a bit after the end of a bit_vector.

For example:

 bit_vector<> v (4) ; 
 v = "000";
 v.push_back(true) ;
 cout << v << endl ; 

This code would produce this output:

 1000