[Boost-users] Implementation question about boost::circular_buffer and allocator

From: Peter Barker (newbarker_at_[hidden])
Date: 2008-08-20 10:42:21

Hello,
 
I've been going through the Boost libraries and encountered boost::circular_buffer. My question is not with the operation of Boost.Circular Buffer as-such, but about how the instantiation of it works without specifying the allocator.
 
The introductory example in the documentation(http://www.boost.org/doc/libs/1_35_0/libs/circular_buffer/doc/circular_buffer.html#briefexample) contains the following line:
 
     // Create a circular buffer with a capacity for 3 integers.
     boost::circular_buffer<int> cb(3);
 
But looking at the header file base.hpp in the circular_buffer directory, we have the following:
 
template <class T, class Alloc>
class circular_buffer
{
......
 
};
 
The Alloc template parameter is not a default one, so I can't understand how we can instantiate cb in the example?
 
Apologies if this is not strictly boost-user related.
 
Regards,
 
Jim