Neil Groves:

This compiler error is to be expected because your code is calling the size() member function. The size() member function requires that the underlying range is a model of the RandomAccessRange Concept. Since you are using a sub_range of a std::list and the std::list has bidirectional iterators, the sub_range is a model of the BidirectionalRange Concept.

This has changed between boost versions. The boost::size(Range&) function was modified to only work with ranges that model the RandomAccessRange Concept because the performance complexity was inconsistent with typical expectations. For example, in your case the sub_range size would have been O(N) despite the container probably having an O(1) implementation of size(). The complexity of std::list size() is not mandated by the standard to be O(1), even though it is recommended. If one wishes to pay the price and wishes to have a more general 'size' calculation I recommend using boost::distance(Range&).

Thanks. I found this thread which is closely related to what I'm wondering. http://boost.2283326.n4.nabble.com/Distance-size-of-boost-ranges-for-std-set... I haven't checked into this much, but would using boost::distance when the underlying container is a deque or vector, be slower than using the container's size? Regards, Brian Wood Ebenezer Enterprises http://webEbenezer.net