#include <boost/bit_logic/bit_container.hpp> 
  bit_handle select ( size_type bit_idx ) ; 
  bit_handle select ( size_type upper_bit_idx , size_type lower_bit_idx ) ;

Note: These functions are equivelant for all bit_container types. bit_array<N>, bit_vector, bit_container_adaptor

The select() function returns a bit_handle, which is a class that refers to some individual bit, or range of bits within a bit container. The bit_handle object has all the same functions as a bit_container.

For example:

 bit_vector<> v (9, true);
 cout << v.select(4) << endl ;						  
 v.select(7,1).flip();
 cout << v << endl ;
 v.select(6,2).flip();
 cout << v << endl ;						  
 v.select(5,3).flip();
 cout << v << endl ;
 v.select(4).flip();
 cout << v << endl ;

This code would produce this output:

 1			
 100000001
 101111101
 101000101
 101010101

Arguments out of range or in wrong order throw exceptions.

std::logic_error	Backwards ordering of range selction
bit_logic::bit_out_of_bounds	Index exceeds boundaries of container