Hi, Are there any proto-based ideas for the library-in-a-week sessions? If not, would building a fixed-point data type be of interest? The domain is narrow enough that something useful can be accomplished in 4 sessions, but of large enough scope to present opportunities for exploring proto in depth. A fairly simple design follows representing a number: fixed_number<int width, int ulp, // 2^{ulp} is the smallest increment possible bool signed, template assigner<first, last, signed> > 'assigner' handles rounding/truncation/wrapping/etc when assigning another number (floating-point or fixed-point) to the current one. Internally, each fixed-point number would be represented by a boost::uint64_t or a boost::int64_t (limiting the maximum precision allowed). As an example, fixed_number<5, -3, false> would represent a data type that would go from 0 to 3.875 in steps of 0.125. Proto would be used for creating all arithmetic operations since the return type of a+b could be different from the type of either a or b. A bonus would involve getting the fixed-point data type to play well with std::complex (and, yes, I am aware that std::complex is not designed to work with anything other than double and float, and will require specialization in the std namespace). If there is sufficient interest, I could even provide a starting point with +,-,* implemented; / would take more time. The design above is intended as a starting point for discussion and I am most definitely not wedded to it. I am a tyro when it comes to proto, and hence would need someone with more proto expertise to guide the discussion. Regards, Ravi