decltype type deduction

decltype_deduction.cpp

// ----------------------------------
// example 1
const int i = 0;            // decltype(i) is const int
bool f(const Widget& w);    // decltype(w) is const Widget&
                            // decltype(f) is bool(const Widget&)

struct Point {
  int x, y;                 // decltype(Point::x) is int
}                           // decltype(Point::y) is int

Widget w;                   // decltype(w) is Widget

std::vector<int> v;         // decltype(v) is std::vector<int>
                            // decltype(v[0]) is int&