c ++ 11：在c ++中创建0到N的constexpr数组 [英] c++11: Create 0 to N constexpr array in c++

问题描述

你好，我在学习C ++ 11，我想知道如何使一个constexpr 0到n数组，例如：

Hello i'm learning C++11, I'm wondering how to make a constexpr 0 to n array, for example:

n = 5;

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

所以数组可以是 {0,1,2,3,4， 5}

推荐答案

与您对问题的意见中的答案不同，

Unlike those answers in the comments to your question, you can do this without compiler extensions.

#include <iostream>

template<int N, int... Rest>
struct Array_impl {
    static constexpr auto& value = Array_impl<N - 1, N, Rest...>::value;
};

template<int... Rest>
struct Array_impl<0, Rest...> {
    static constexpr int value[] = { 0, Rest... };
};

template<int... Rest>
constexpr int Array_impl<0, Rest...>::value[];

template<int N>
struct Array {
    static_assert(N >= 0, "N must be at least 0");

    static constexpr auto& value = Array_impl<N>::value;

    Array() = delete;
    Array(const Array&) = delete;
    Array(Array&&) = delete;
};

int main() {
    std::cout << Array<4>::value[3]; // prints 3
}

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