0
如果爲0
,則按預期工作(從列表中獲取索引類型)。如果1 static_assert()
總是跳閘。我會認爲static_assert()
只會發生在所有的typename
都用完了。爲什麼不是這樣?爲什麼`static_assert`總是被調用?
#define USE_STATIC_ASSERT 1
template <unsigned int I, typename ...Ts>
struct items;
template <typename T, typename ...Ts>
struct items<0, T, Ts...>
{
typedef T type;
};
template <unsigned int I, typename T, typename ...Ts>
struct items<I, T, Ts...> : items<I-1, Ts...>
{
};
#if USE_STATIC_ASSERT
template <unsigned int I>
struct items<I>
{
static_assert(false, "Ran out of Ts.");
};
#endif
int main()
{
cout << is_same<float, items<1, int, float, double>::type>::value << endl;
}