RE: [Boost-users] Re: map with minimal memory footprint

From: Jim.Hyslop (Jim.Hyslop_at_[hidden])
Date: 2005-03-22 14:50:19

Gottlob Frege wrote:
> I believe you, but can you explain what you mean by "iterator
> invalidation properties".  I wrote a vector_map once, and it was as
> "map-ish" as needed at the time, so I suspect it was just a "useful
> associative container", but I'm just curious as to what I was
> missing...
When you insert or erase elements in a container, The Standard imposes
requirements on what happens to iterators and references you have to
elements in a container.

All map iterators and references must remain valid after inserts. After
erasing, only iterators and references to the erased element are allowed to
be invalidated.

Inserts into vectors (including via 'resize' or 'reserve') can invalidate
all references and iterators, if the vector has to reallocate; otherwise,
only references and iterators to elements prior to the one being inserted
remain valid. Erasing invalidates iterators and references to elements after
the one being erased.

If you have a copy of the Standard, search for "invalidate" in section 23
for full details.

-- 
Jim Hyslop
Senior Software Designer
Leitch Technology International Inc. ( http://www.leitch.com )
Columnist, C/C++ Users Journal ( http://www.cuj.com/experts )