Is it possible to create and initialize an array of values using template metaprogramming?

Question

I want to be able to create an array of calculated values (let\'s say for simplicity\'s sake that I want each value to be the square of it\'s index) at compile time using t

Answer 1

You can have that for fixed-size arrays:

int a[] = { foo<0>::value, foo<1>::value, ... };

Arbitrarily sized arrays however can't be done without preprocessor meta-programming - Boost.Preprocessor can help here.

Another thing you might want to look into are compile-time sequences of integral constants, e.g. using Boost.MPL:

template
struct squares {
    typedef typename squares::type seq;
    typedef typename boost::mpl::integral_c::type val;    
    typedef typename boost::mpl::push_back::type type;
};

template<>
struct squares<1> {
    typedef boost::mpl::vector_c::type type;
};

// ...
typedef squares<3>::type sqr;
std::cout << boost::mpl::at_c::type::value << std::endl; // 1
std::cout << boost::mpl::at_c::type::value << std::endl; // 4
std::cout << boost::mpl::at_c::type::value << std::endl; // 9

(Note that this could probably be done more elegantly using MPLs algorithms)

If you're more curious about the compile-time subject the books "Modern C++ Design" (TMP basics) and "C++ Template Metaprogramming" (mainly MPL explained in depth) are worth looking into.