[boost] intrusive list

From: Geoff Carlton (gcarlton_at_[hidden])
Date: 2005-06-23 19:42:41

I've just come across the intrusive list class in the sandbox.  I've 
been searching for a class like this for quite some time, but I never 
thought to look through the boost sandbox area for it.  I can finally 
ditch my own partial implementation and use this nice alternative!

One issue I have seen with this class is that it destroys its nodes on 
list destruction.  Previously implementations I have seen instead 
assert(empty()), leaving it up to the programmer to explicitly decide 
what to do.  In some cases it is indeed to clear the list, but in others 
it may be to dethread the list and do something else entirely with the 
nodes.

An example is in the common pattern:
    array<particle> myPool;
    ilist<particle> activeList;
    ilist<particle> freeList;
Under this scheme the nodes were allocated in the array and then 
threaded onto their respective lists.  As such, automatic deletion would 
cause a crash, and the programmer should instead just "leak" the list 
back into the array.

Another disadvantage of the destructor calling clear() is that it 
prevents the node class from having a private destructor.  Objects may 
need to be deleted via a manager class, however the destructor's clear() 
will cause a compile error in this situation.

I find it interesting that under the "move sematics" C++0x proposal, the 
ilist could be given move sematics and thus fit into STL containers.  Is 
there any ongoing interest in this class, and will it eventually make it 
into the boost proper?

Geoff