How to get element from circular_buffer

I am using boost library in MAC (xcode). I have two questions about boost::circular_buffer.

1 - I am getting syntax error when declaring the circular_buffer

boost::circular_buffer<int> cb(10);

Expected parameter decelerator
Expected ')'

2 - Second question is when I add element into boost::circular_buffer using push_back, how to extract / get the element from circular_buffer, pop_front does not give the element.

boost::circular_buffer<T>::front() gives you a reference to the element at the "front", while boost::circular_buffer<T>::pop_front() will remove that element.

boost::circular_buffer<T>::back() gives you a reference to the element at the back, while boost::circular_buffer<T>::pop_back() removes that element.

It appears your syntax error is resulting from the most vexing parse. Try instead:

boost::circular_buffer<int> cb;
cb.set_capacity(10); 

Or more succinctly:

boost::circular_buffer<int> cb((10));