auto int i = 0 //C++98

auto x = 5 //x --> int
auto pi = new auto(1) //pi --> int*
const auto *v = &x, u = 6 //v --> const int* 、 u --> const int
static auto y = 0.0 //y --> double
int x = 0
auto * a = &x //a --> int* , auto為int
auto b = &x //b --> int* , auto 為 int*
auto c = x //c --> int& , auto為int
auto d = c //d --> int , auto為int
const auto e = x //e --> const int
auto f = e //f --> int
const auto& g = x //g --> const int&
auto& h = g //h --> const int&

for(auto it = resultMap.begin(); it != resultMap.end(); ++i){
//do something
}

class Foo{
public:
static int get(void)
{
return 0;
}
};
class Bar{
public:
static const char* get(void)
{
return "0";
}
};
template<class A>
void func(void)
{
auto val = A::get();
// ...
}

int x = 0
decltype(x) y = 1 //y -> int
decltype(x + y) z = 0 //z -> int
const int& i = x
decltype(i) j = y //j -> const int &
cosnt decltype(z) *p = &z //*p -> const int, p -> const int *
decltype(z) * pi = &z //*pi -> int , pi -> int*
decltype(pi) * pp = &pi //*pp -> int * ,pp -> int **

typedef decltype(nullptr) nullptr_t
typedef decltype(sizeof(0)) size_t
`

vector<int> v;
decltype(v):value_type i = 0

template<class ContainerT>
class Foo
{
decltype(ContainerT().begin()) it_;
public:
void func(ContarinerT& container)
{
it_ = container.begin();
}
// ...
}

int & foo(int& i);
float foo(float& f)
template<typename T>
auto fun(T& val) -> decltype(foo(val))
{
return foo(val);
}