[Boost-users] ptr_sequence and transfer functions.

From: Matthew Bray (mat_at_[hidden])
Date: 2007-03-20 09:37:16

I have a problem with the current ptr_sequence interface, according to 
the documentation point #7 at this location:
http://www.boost.org/libs/ptr_container/doc/examples.html#transferring-ownership-of-pointers-between-different-pointer-containers

it should be possible to write something such as this

ptr_list<X> list; ptr_vector<X> vec;

list.transfer( list.begin(), vec.begin(), vec );
vec.transfer( vec.end(), list.begin(), list.end(), list );

i.e. given a U<T> and a V<T> I should be able to perform transfer 
operations in either direction.

However given a suitable X this code fails to compile on VC++ 8 as well 
as GCC 3.4. Indeed any attempt to transfer between different 
ptr_sequence types (e.g. ptr_deque<X> to ptr_vector<X>) fails to 
compile. Looking at the implementation of ptr_sequence it appears easy 
to see why this is the case. However my question is is the documentation 
incorrect or is the current code incorrect?

Right now if I wish to create containers of objects and then transfer 
ownership to others I'm forced to use the same container type throughout 
(i.e. the transfer functions provide no benefit at all if I have to 
choose the wrong container for the job), either that or write awkward 
transferal code when it appears the simple transfer function should do 
the job.

Could someone please explain the situation regarding the transfer 
functions and documentation at this time?

Thanks, Mat.