REALLY_STRONG_TYPEDEF

really_strong_typedef.cc

#include <type_traits>
#include <iostream>

#define REALLY_STRONG_TYPEDEF(From, To)                 \
  class To final {                                      \
    static_assert(std::is_scalar<From>(), "");          \
    From x;                                             \
                                                        \
   public:                                              \
    To() = default;                                     \
    explicit To(From x_) : x(x_) {}                     \
    explicit operator From&() { return x; }             \
    explicit operator const From&() const { return x; } \
  };                                                    \
  inline From from##To(To to) { return static_cast<From>(to); }

REALLY_STRONG_TYPEDEF(int, Latitude)
REALLY_STRONG_TYPEDEF(int, Longitude)

// you still can extend the types
inline bool operator<(Latitude lhs, Latitude rhs) {
  return fromLatitude(lhs) < fromLatitude(rhs);
}

void fn(const Latitude& lat, const Longitude& lon) {
  std::cout << fromLatitude(lat) << " " << fromLongitude(lon) << std::endl;
}

int main() {
  Latitude lat{48};
  Longitude lon{12};

  fn(lat, lon);

  // accidentally mixing arguments fails at compile time
  // fn(lon, lat);

  // initialization from different type fails at compile time
  // lat = lon;

  // implicit conversion fails at compile time
  // lat += 2;

  // NOTE: Boost's STRONG_TYPEDEF allows the last two to compile!
  
}