I wrote an implementation which removes the Allocator parameter of boost::function: http://www.revergestudios.com/boost-function/ All tests pass on msvc 7.1, 8.0, and gcc 3.4.4 (I had to modify the allocator test.) To try my implementation, you'll need the rest of the boost::function files from CVS HEAD. Allocators are supported as an argument to the following boost::function constructor: template<typename Functor,typename Allocator> function(Functor f, Allocator a); A copy of the passed allocator is stored in the boost::function object, the same way it's done in shared_ptr. Notes: 1) As in the current official boost::function implementation, the allocator is only used if the boost::function object is initialized with a function object which does not fit in a "small" static buffer. 2) When a function object that can not use the small object optimization is assigned (by operator=) to an existing boost::function object, the boost::function object will not have an allocator and will use new/delete. To allow users to supply an allocator in an assignment operation, I added a new member function: template<typename Functor,typename Allocator> void assign(Functor f, Allocator a); Emil Dotchevski ----- Original Message ----- From: "Douglas Gregor" <doug.gregor@gmail.com> To: <boost@lists.boost.org> Sent: Tuesday, June 05, 2007 10:46 AM Subject: Re: [boost] [function] allocator template parameter question
On Jun 5, 2007, at 12:42 PM, Emil Dotchevski wrote:
On Jun 4, 2007, at 10:57 PM, Emil Dotchevski wrote:> > 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?> > You know, I never even thought about adding it. I didn't know about > the shared_ptr technique when I put the allocator into > boost::function, and after the C++ committee removed the allocator I > didn't think about it any more. Perhaps if the allocator it's moved to the constructor, the committee would accept it? :)
Since shared_ptr already has this functionality in its constructor, they may accept it. You could certainly write a short proposal to the C++ committee...
<snip>> I don't know when I would have time to implement this, although I > would certainly consider adding this functionality to Boost's > "function". Might you be interested in implementing it? OK, I'll give it a shot, and I'll let you know how it goes.
Great!
- Doug _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost