[boost] [function] allocator template parameter question

From: Emil Dotchevski (emildotchevski_at_[hidden])
Date: 2007-06-04 22:57:35

One important advantage of using boost::function is that it acts like a 
function pointer, reducing physical coupling between compilation units. This 
is very much like shared_ptr.

A nice feature of shared_ptr is that it has a single template parameter, T, 
even though diferent instances of shared_ptr<T> can use different 
allocators.

When using boost::function, one can also provide an allocator, but unlike 
shared_ptr, the allocator is a default parameter of the boost::function 
class template.

Is there a reason why this is necessary? Can't boost::function use similar 
technique to the one employed by shared_ptr to avoid the need for this 
second template parameter?

Emil Dotchevski