Cryolite

#include <type_traits>

void f(std::integral_constant<int, 0>);

template<int I>
auto f(std::integral_constant<int, I>)
  -> decltype(f(std::integral_constant<int, I - 1>()));

int main()
{

Cryolite

#include <iostream>


struct S
{
  S(int i) : i_(i) {}
  S(S const &) = delete;
  S(S &&) = delete;
  void double_() { i_ *= 2; }
  int get() const { return i_; }

Cryolite

#include <functional>
#include <iostream>


class C
{
public:
  C() : i_() {}
  std::function<void(int)> set = [this](int i) mutable { this->i_ = i; };
  std::function<int()>     get = [this]() { return this->i_; };