可变参数模板

1. sizeof...计算参数个数

template<typename... Ts>
void magic(Ts... args) {std::cout << sizeof...(args) << std::endl;
}

2.递归模板函数

template<typename T>
void printf1(T value) {std::cout << value << std::endl;
}template<typename T, typename... Ts>
void printf1(T value, Ts... args) {std::cout <<"剩余参数:" <<sizeof...(args)<< "," << value << std::endl;printf1(args...);
}int main() {printf1(1, 2, "123", 1.1);return 0;
}

3.C++17 中增加了变参模板展开的支持

//C++17 中增加了变参模板展开的支持
template<typename T0, typename... T>
void printf2(T0 t0, T... t) {std::cout << t0 << std::endl;if constexpr (sizeof...(t) > 0) printf2(t...);
}

4.初始化列表展开

template<typename T, typename... Ts>
auto printf3(T value, Ts... args) {std::cout << value << std::endl;(void) std::initializer_list<T>{([&args] {std::cout << args << std::endl;}(), value)...};
}