用递增的数字初始化一个编译时常量大小的数组 [英] initialize an array of compile-time constant size with incrementing numbers

问题描述

我有一个数组，其大小是使用编译时常量设置的（在我的情况下为预处理器 #define ）。我需要在编译时使用连续的数字对其进行初始化。我该怎么做？

I have an array whose size is set using a compile-time constant (a pre-processor #define in my case). I need to initialize it using consecutive numbers at compile-time. How can I do this?

简化示例：

#define ARR_SZ 5
struct C {
  C(int a) : a(a) {}
  int a;
};
C arr[ARR_SZ] = {{0},{1},{2},{3},{4}}; // This needs to adapt to any number

我可以使用C ++ 11，但不能使用较新的（尽管即使我不能在项目中使用较新的技术，我也会对此感兴趣。）

I can use C++11, but not newer (although I would be interested to learn of newer techniques even if I can't use them for this project)

推荐答案

C ++ 14个代码（由于 std :: integer_sequence ）：

C++14 code (because of std::integer_sequence):

#include <type_traits>
#include <array>

#define ARR_SZ 5
struct C {
  C(int a) : a(a) {}
  int a;
};

template<int ...Is>
auto make_C_arr(std::integer_sequence<int, Is...>) -> std::array<C, sizeof...(Is)> {
    return {{ {Is}... }};
}

auto arr = make_C_arr(std::make_integer_sequence<int, ARR_SZ>{});

int main () {

}

std :: integer_sequence 等可在C ++ 11中实现，但是如注释中所述，因此将标准版本替换为自制的版本将得到C ++ 11特定解决方案。

std::integer_sequence and the like are implementable in C++11 however as noted in a comment, so substituting the standard version for a home-brewed one will give a C++11 specific solution.

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