cpp-opaque-typedef/include/opaque_typedef/comparable.hpp

#pragma once

namespace types {
  template <typename Self> struct EqualityComparable {
    friend bool operator==(Self const & lhs, Self const & rhs) {
      return lhs.get() == rhs.get();
    }
    friend bool operator!=(Self const & lhs, Self const & rhs) {
      return !(lhs == rhs);
    }
  };

  template <typename Self> struct Comparable : EqualityComparable<Self> {
    friend bool operator<(Self const & lhs, Self const & rhs) {
      return lhs.get() < rhs.get();
    }
    friend bool operator>(Self const & lhs, Self const & rhs) {
      return rhs.get() < lhs.get();
    }
    friend bool operator<=(Self const & lhs, Self const & rhs) {
      return !(rhs.get() < lhs.get());
    }
    friend bool operator>=(Self const & lhs, Self const & rhs) {
      return !(lhs.get() < rhs.get());
    }
  };
}