c++11新特性--auto

auto 关键字

auto i = 5    // i will be of type int

int n=3;
double pi=3.14;
auto j=pi*n;    // j will be of type double

// take a hypothetical Map of ( int and an map(int,int) )
map< int, map<int,int> > _Map;
// see the verbose for defining a const iterator of this map
map<int, map<int,int>>::const_iterator itr1 = _Map.begin();
 // now with auto our life gets simplified
const auto itr2 = _Map.begin();

template<class U, class V>
void Somefunction(U u, V v)
{
??? result = u*v; // now what would be the type of result ???

    // with auto we leave the compiler to determine the type
    auto result = u*v;
}

auto k = 5;
auto* pK = new auto(k);
auto** ppK = new auto(&k);
const auto n = 6;

auto m; // m should be intialized

auto int p; // no way

void MyFunction(auto parameter){} // no auto as method argument

template<auto T> // utter nonsense - not allowed
void Fun(T t){}

int* p = new auto(0); //fine
int* pp = new auto(); // should be initialized

auto x = new auto(); // Hmmm ... no intializer

auto* y = new auto(9); // Fine. Here y is a int*
auto z = new auto(9); //Fine. Here z is a int* (It is not just an int)

int value = 123;
auto x2 = (auto)value; // no casting using auto

auto x3 = static_cast<auto>(value); // same as above

auto x1 = 5, x2 = 5.0, x3='r';  // This is too much....we cannot combine like this

    const int i = 99;auto j = i;       // j is int, rather than const intj = 100           // Fine. As j is not constant// Now let us try to have referenceauto& k = i;      // Now k is const int&k = 100;          // Error. k is constant// Similarly with volatile qualifer

  int a[9];auto j = a;cout<<typeid(j).name()<<endl; // This will print int*auto& k = a;cout<<typeid(k).name()<<endl; // This will print int [9]

引自codeproject，仅供个人参考