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"It's time to abandon the traditional, but inaccurate, ideas of what it means to be object-oriented. Are you a true encapsulation believer? If so, I know you'll embrace non-friend non-member functions with the fervor they deserve."

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Think STL! Think STL algorithms! :-)

Just for the record, I agree with Joel. Who is still writing old style OO "c++" libraries any more. I'm suprised that it is even being proposed here on boost. Please study boost::gil (from adobe) or boost::spirit to understand what a well written modern c++ library looks like.