On Nov 20, 2006, at 7:48 AM, John Maddock wrote:
As an aside, I've always wanted a sort of "conceptual" std lib implementation, that included in each header nothing except what absolutely has to be there. Just the declarations would do, so we could do compile-time tests against it to verify inclusion of the right headers: the only tricky bit is getting the compile time constants correct so that it can still compile meta code. Any volunteers? :->
One of the problems with this project is deciding exactly what should appear in the headers. For example, imho, this is a valid C++ program: #include <iostream> int main() { std::cout << "Hello World\n"; } In order for that to be valid, <iostream> must declare and define the namepace scope: template<class traits> basic_ostream<char, traits>& operator<< (basic_ostream<char, traits>& out, const char* s); which lives in <ostream>. In other words, I think it would be incorrect for <iostream> *not* to include <istream> and <ostream>. I have heard people argue that HelloWorld should include <ostream> explicitly as well. But imho that leads to a C++ language spec that is just too difficult and cumbersome to use (and we're already at risk for that reputation). So to catch this particular bug (mistaken uses of <iostream>) we would need a tool that looked for std::ios_base::Init constructors in the translation unit, but no uses of one of the eight terminal streams. Outside of a grep-like tool operating on the preprocessed translation unit (as an extra compilation phase), I'm not sure how to catch that with a std::lib implementation or prototype. Seems like something the compiler could do no problem though. :-) -Howard