Re: CMap - can it do this?
"Doug Harrison [MVP]" <dsh@mvps.org> wrote in message
news:7t5l44ldqq9rt9lbdl21ch07vn5b7sv4ic@4ax.com...
Maintaining state in a collection during iteration tends to cause problems
for thread safety and "nested" iteration by a single thread, so on general
principle, I'd be very surprised if that was done. It would be much better
to provide an erase(POSITION) member function instead.
If a POSITION is a pointer to the actual value, I can't see how caching it
causes concurrency issues, anymore than generally accessing the entire
dictionary across threads. Elaborate?
I hope it's not the only one. What CMap should support is an erase
function
that takes a POSITION, but POSITION objects seem useful only as magic
cookies in CMap's bizarre iteration model.
But erasing all elements in the dictionary is but one reason for iterating
through it. What about the general pattern of iterating each key, then
using its value? .NET collections can iterate and return the value of each
item along with the key, so you don't have to lookup by key in order to get
the value. But this code is more complex code. I was hoping to write the
simple code that dereferenced the iterated key in order to get the value and
hope that the dictionary would be smart enough to realize that I would soon
be asking for the value when it gave me the key in the iterator. Maybe not.
-- David