Question

Is it possible in C++ to determine number of variables/fields in the generic class?
for example

// suppose I need metaclass number_members determines number of members

struct example { int i, j; };
assert(number_members<example>::value==2);

I looked through mpl but could not find implementation.

thanks.

Answer 1

No. C++ does not provide general introspection into structures.

You can try a C++0x std::tuple, which has some of the features of a general POD struct. Or, try to roll your own from the Boost MPL library. That would be a bit advanced if you’re just getting started with C++.