Jeremy Day wrote:
All,
I have been following this discussion and I would like to just add a general point. I have been trying to grok template metaprogramming off and on for a while now, and I think that the leap from object-oriented programming to template metaprogramming is a good deal larger than the leap from procedural programming to object-oriented programming.
That's been my experience, too. Template metaprogramming is like an alternate universe where the 'normal' rules no longer apply. For example, take something like this: template <typename X> X divide_em(X x, X y) { if (typeid(x) == typeid(std::string)) return x; else return x/y; } std::cout << divide_emstd::string("one", "two"); It's hard at first to understand why this code doesn't work. It takes a real paradigm shift to see it not as an executable would (x is a string, so take the 'if' path and ignore the 'else' path), but as the compiler would (construct a function whose last line divides two strings). I'm afraid I can't comment on MPL, either the book or the library. I'd assumed that there wasn't much point in even looking at it until I was completely comfortable with metaprogramming. Reading this thread has made me question that assumption. Is MPL appropriate for metaprogramming newbies?