How Can C 11 and C 14 Be Used to Create Compile-Time Constant Arrays?

Crafting Constexpr Arrays in C 11: A Walkthrough

In the realm of C programming, occasionally we encounter situations where we need to define an array with constant values during compile-time. This is especially useful when dealing with arrays of known size that won't change during runtime. C 11 offers a powerful feature known as constexpr that enables us to create such arrays.

Consider the following scenario: you want to define an array of integers from 0 to a specified value, 'n'. In C , we can typically express this as:

int n = 5;
int array[] = {0 ... n};

However, in C 11, we can achieve this same result using constexpr, ensuring that the values are known at compile-time.

Embracing C 14 for Efficient Initialization

C 14 introduces a paradigm shift that streamlines the process of creating constexpr arrays. Utilizing a constexpr constructor and a loop, we can effortlessly initialize an array like so:

#include <iostream>

template<int N>
struct A {
    constexpr A() : arr() {
        for (auto i = 0; i != N; ++i)
            arr[i] = i; 
    }
    int arr[N];
};

int main() {
    constexpr auto a = A<4>();
    for (auto x : a.arr)
        std::cout << x << '\n';
}

In this code snippet, the constexpr constructor initializes the arr array with values ranging from 0 to N-1 during compile-time. This technique ensures efficient creation of constexpr arrays, maximizing performance and reducing runtime overhead.

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