cpp11 的变量类型自动推断

1. decltype作用是变量类型推断：auto test(){return std::make_tuple("Hello World!", 'a', 3.14, 0);}int main(){auto x = test();  constexpr size_t sz = tuple_size<decltype(x)>::value;const int ci = 0, &cj = ci;decltype(ci) x = 0;decltype(cj) y = x;     return 0;}2. autovector<int> ivec = { 1,2,3,4,5,6,7,8,9,10 };//for (auto it = ivec.begin(); it != ivec.end(); ++it)//*it = (*it) * 2;for (auto& i : ivec)i *= 2;for (auto i: ivec)cout << i << endl;