Can metaprogramming techniques be used to programmatically assign values to static arrays at compile time in C ?

Programmatic Array Creation at Compile Time in C

C provides the ability to define static arrays at compile time using explicit declarations like:

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

Question 1: Programmatic Value Assignment

Can metaprogramming techniques be utilized to assign values to these elements programmatically at compile time?

Answer:

C 0x introduces the concept of template variadic arguments, allowing the initialization of arrays from a variable number of arguments. However, template instantiation depth limits the practicality of this approach for large arrays.

Question 2: Selective Value Assignment

Assuming most array elements are the same, can values be selectively assigned in a programmatic manner at compile time?

Answer:

A more refined approach utilizes C 0x metafunctions and template specialization to generate arrays with interspersed values. This involves a recursive template struct generate_array and a custom metafunction MetaFunc to define element values.

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";
}

This solution involves recursive template instantiation and is suitable for arrays of limited size due to template depth limitations.

The above is the detailed content of Can metaprogramming techniques be used to programmatically assign values to static arrays at compile time in C ?. For more information, please follow other related articles on the PHP Chinese website!