Off topic. Feel free to ignore. About baby template meta-programming. Working my way through "C++ Template Metaprogramming" by Abrahams and Gurtovoy, and am doing exercise 2-3/4. This: template<typename T,size_t D> struct type_descriptor<T[D]> { static std::ostream& print(std::ostream& os) { os << type_descriptor<T>() << '[' << D << ']'; return os; } }; When asked to deal with a type, for example, char[7][8][9] results in the reversal of the indices and prints char[9][8][7]. I can deal with that, (see the p.s. at the end), but it made me curious. That implies that the compiler is seeing it like ((char[9])[8])[7] which makes sense. It's an array of length 7 of arrays of length 8 of arrays of length 9 characters. That's C/C++ row-major order. It has 7 tables each of which has 8 rows of 9 characters. My question is this. Can I count on this? I don't mean row-major order, I mean that the compiler will always match in this order. Is this matching BECAUSE of row-major order, or is it compiler dependent? Wait, never mind. I just thought it through. The implication, if it had done it textually as I expected, is that T would have had type char[7][8], and the second time, T would have had type char[7] which would have been a completely different beast. Well. I'm not really asking the question now after all, just throwing this out in case it helps anyone else's understanding. Please feel free to ignore. lol! I'm also implementing all of the is_char, is_array, remove_reference etc. metafunctions instead of using the boost or c++0x ones. I figure that way by the time I get through the book I'll have more understanding. That has given me questions, because after I implement each one, I look at the boost implementation, and I look at the the gcc libstdc++ implementation of the c++0x ones and generally they are, in order of reducing complexity, boost, gcc, me. Some of the difference in complexity is that boost needs to work with different compilers on different architectures, and gcc has to work with different architectures, and I just have to get it to compile on my machine (ubuntu maverick meercat on a dell inspiron 1420 laptop) with the gcc compiler (last night's pull from trunk) that I'm using. Other times, though, it LOOKS to me like there's extra complexity for nothing (I think brought about by the desire for maximal code reuse, i.e. don't include something in your template when you can invoke another cool metafunction to do it for you, but at the expense of higher compile-time complexity). I'll hold off on questions like that, though, until I finish the book in case the answers are in there. ;p Patrick p.s. if anyone cares, here's what I came up with (with the char base type type_descriptor so you can do std::cout << type_descriptor[7][8][9]). Any comments, improvements, critiques, and alternate implementations welcome: template<typename T> struct print_dimensions { // handles exit condition for recursive print_dimensions static std::ostream& print(std::ostream&os) { return os; } }; template<typename T,size_t D> struct print_dimensions<T[D]> { static std::ostream& print(std::ostream&os) { // print our dimension and invoke ourselve recursively to do the next os << '[' << D << ']'; print_dimensions<T>::print(os); return os; } }; template<typename T> struct remove_all_dimensions { // when no more dimensions this is the stop condition for the recursion typedef T type; }; template<typename T, size_t D> struct remove_all_dimensions<T [ D ]> { // recurse to ask our type with one less dimension to define the type for us typedef typename remove_all_dimensions<T>::type type; }; template<typename T> struct type_descriptor<char> { static std::ostream& print(std::ostream& os) { os << " char"; return os; } }; template<typename T,size_t D> struct type_descriptor<T[D]> { static std::ostream& print(std::ostream& os) { // pull off all the dimensions, print the base type, then ask print_dimensions to print the dims. os << type_descriptor<typename remove_all_dimensions<T>::type>(); print_dimensions<T[D]>::print(os); return os; } }; p.p.s This is really fun! p.p.p.s Does anyone know of a mailing list to discuss beginning TMP? Patrick again ;p