c++ 编译器字符串拼接

strcat是发生在运行期,如何在编译期进行字符串拼接呢,下边是相关代码实例:

#include 
template
struct charArray
{
	static const char *to_array()
	{
		static const char arr[sizeof ...(ch) + 1] = {ch...};
		return arr;
	}
};
template
struct concat{};

template
struct concat, charArray>
{
     static const char* to_array(){
		return charArray::to_array();
	}
};
int main()
{
	std::cout<::to_array()<::to_array()<, charArray<'e', 'f', 'g'>>::to_array()<