函数参数的算术和

Question

请注释代码在我执行此已知任务时出现的问题

template <typename T>
T arithmetic_sum(T first) {
    return first;
}

template<typename T, typename... Types>
auto arithmetic_sum(T first, Types ...others) ->decltype(first + arithmetic_sum(others...)) {
    return first + arithmetic_sum(others...);
}

（GCC 4.9）

e.g。这个电话

auto i = arithmetic_sum(123, 123.45, 0.55l);

无法编译错误：

错误：没有匹配函数来调用＆＃39; arithmetic_sum（int，double，long double）＆＃39;

auto i = arithmetic_sum（123,123.45,0.55l）;                                                             ^