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From: Beman Dawes (bdawes_at_[hidden])
Date: 2001-11-20 19:08:19

At 12:05 PM 11/20/2001, Carl Daniel wrote:

>Funny you should ask...
>I have implemented a B+Tree class which (mostly) emulates the std::map
>interface, and which supports huge content with easily constrained use
>of memory.

I have used a B+Tree implementation very effectively for years. It's
cursor based rather than iterator based.

An STL-like version with iterators seemed like a natural for Boost, so I
put together an initial implementation. But I ran into several worrisome
issues which sidetracked me. The worst was the question of validity of
pointers and references after iterator destruction. See This has
finally been resolved, but until library suppliers change their reverse
iterator implementations, use of a reverse iterator on a B-tree will be

The POD requirement was also a problem; before the current Boost type
traits I didn't know of any way to assert that the requirement was being
met, and was scared of the fallout from that.

To sum up, I think a B+Tree would be wonderful, but am worried if it
deviates from associative container requirements in too many subtle ways,
particularly if any of its unique requirements could result in errors
undetectable at compile time.


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