c++元编程打印二叉树

#include<iostream>
using namespace std;

template<typename T,T val,typename L,typename R>
struct Tree {
    
    };

template<typename T>
struct Print {
    
    };
template<typename T, T val,typename L, typename R>
struct Print<Tree<T,val,L,R> >{
    
    
	static void print() {
    
    
		cout << val<<' ';
		if constexpr (is_void<L>::value == false) {
    
    
			Print<L>::print();
		}
		if constexpr (is_void<R>::value == false) {
    
    
			Print<R>::print();
		}
	}
};

int main() {
    
    
	Print<Tree<int, 3, Tree<int, 4, void, void>, Tree<int, 5, void, void>>>::print();
}