Question

One can define a static array at compile time as follows:

const std::size_t size = 5;    
unsigned int list[size] = { 1, 2, 3, 4, 5 };

Question 1 – Is it possible by using various kinds of metaprogramming techniques to assign these values “programmatically” at compile time?

Question 2 – Assuming all the values in the array are to be the same barr a few, is it possible to selectively assign values at compile time in a programmatic manner?

eg:

const std::size_t size = 7;        
unsigned int list[size] = { 0, 0, 2, 3, 0, 0, 0 };

1. Solutions using C++0x are welcome
2. The array may be quite large, few
   hundred elements long
3. The array for now will only consist of
   POD types
4. It can also be assumed the size of
   the array will be known beforehand,
   in a static compile-time compliant
   manner.
5. Solutions must be in C++ (no script, no macros, no pp
   or code generator based solutions pls)

UPDATE: Georg Fritzsche’s solution is amazing, needs a little work to get it compiling on msvc and intel compilers, but nonetheless a very interesting approach to the problem.

Answer 1

The closest you can get is using C++0x features to initialize local or member arrays of templates from a variadic template argument list.
This is of course limited by the maximum template instantiation depth and wether that actually makes a notable difference in your case would have to be measured.

Example:

template<unsigned... args> struct ArrayHolder {
    static const unsigned data[sizeof...(args)];
};

template<unsigned... args> 
const unsigned ArrayHolder<args...>::data[sizeof...(args)] = { args... };

template<size_t N, template<size_t> class F, unsigned... args> 
struct generate_array_impl {
    typedef typename generate_array_impl<N-1, F, F<N>::value, args...>::result result;
};

template<template<size_t> class F, unsigned... args> 
struct generate_array_impl<0, F, args...> {
    typedef ArrayHolder<F<0>::value, args...> result;
};

template<size_t N, template<size_t> class F> 
struct generate_array {
    typedef typename generate_array_impl<N-1, F>::result result;
};

Usage for your 1..5 case:

template<size_t index> struct MetaFunc { 
    enum { value = index + 1 }; 
};

void test() {
    const size_t count = 5;
    typedef generate_array<count, MetaFunc>::result A;

    for (size_t i=0; i<count; ++i) 
        std::cout << A::data[i] << "\n";
}