cpp-opaque-typedef/opaque_typedef.hpp

//
//  opaque_typedef.hpp
//  opaque-type
//
//  Inspired by https://foonathan.github.io/blog/2016/10/19/strong-typedefs.html and others
//
//  Created by Sam Jaffe on 8/16/16.
//

#pragma once

template <typename Tag, typename T>
T underlying_type_impl(strong_typedef<Tag, T>);

template <typename T>
using underlying_type = decltype(underlying_type_impl(std::declval<T>()));

#define OPAQUE_TYPE_ASSIGN_OPERATOR(name, op) \
  template <typename TDef> \
  struct name { \
    friend TDef & operator op##=(TDef & lhs, TDef const & rhs) { \
      using type = underlying_type<TDef>; \
      static_cast<type &>(lhs) op##= static_cast<type const &>(rhs); \
      return lhs; \
    } \
    \
    friend TDef operator op(TDef const & lhs, TDef const & rhs) { \
      using type = underlying_type<TDef>; \
      return TDef(static_cast<type const&>(lhs) op static_cast<type const&>(rhs)); \
    } \
  }

#define OPAQUE_TYPE_BINARY_OPERATOR(name, op) \
  template <typename TDef> \
  struct name { \
    friend TDef operator op(TDef const & lhs, TDef const & rhs) { \
      using type = underlying_type<TDef>; \
      return TDef(static_cast<type const&>(lhs) op static_cast<type const&>(rhs)); \
    } \
  }

#define OPAQUE_TYPE_MIXED_BINARY_OPERATOR(name, op) \
  template <typename TDef, typename RDef, typename Out> \
  struct name { \
    friend Out operator op(TDef const & lhs, RDef const & rhs) { \
      using type1 = underlying_type<TDef>; \
      using type2 = underlying_type<RDef>; \
      return Out(static_cast<type1 const&>(lhs) op static_cast<type2 const&>(rhs)); \
    } \
  }; \
  \
  template <typename TDef, typename RDef> \
  struct name<TDef, RDef, TDef> { \
    friend TDef operator op##=(TDef & lhs, RDef const & rhs) { \
      using type1 = underlying_type<TDef>; \
      using type2 = underlying_type<RDef>; \
      static_cast<type1 &>(lhs) op##= static_cast<type2 const&>(rhs); \
      return lhs; \
    } \
    \
    friend Out operator op(TDef const & lhs, RDef const & rhs) { \
      using type1 = underlying_type<TDef>; \
      using type2 = underlying_type<RDef>; \
      return Out(static_cast<type1 const&>(lhs) op static_cast<type2 const&>(rhs)); \
    } \
  }

#define OPAQUE_TYPE_BINARY_OPERATOR(name, op) \
  template <typename TDef> \
  struct name { \
    friend TDef operator op(TDef const & val) { \
      using type = underlying_type<TDef>; \
      return TDef(op static_cast<type const&>(val)); \
    } \
  }

OPAQUE_TYPE_UNARY_OPERATOR(unary_plus, +);
OPAQUE_TYPE_UNARY_OPERATOR(unary_minus, -);

OPAQUE_TYPE_ASSIGN_OPERATOR(addition, +);
OPAQUE_TYPE_ASSIGN_OPERATOR(subtraction, -);
OPAQUE_TYPE_ASSIGN_OPERATOR(multiplication, *);
OPAQUE_TYPE_ASSIGN_OPERATOR(division, /);
OPAQUE_TYPE_ASSIGN_OPERATOR(modulo, %);

OPAQUE_TYPE_MIXED_BINARY_OPERATOR(mixed_addition, +);
OPAQUE_TYPE_MIXED_BINARY_OPERATOR(mixed_subtraction, -);
OPAQUE_TYPE_MIXED_BINARY_OPERATOR(mixed_multiplication, *);
OPAQUE_TYPE_MIXED_BINARY_OPERATOR(mixed_division, /);

OPAQUE_TYPE_ASSIGN_OPERATOR(bitwise_and, &);
OPAQUE_TYPE_ASSIGN_OPERATOR(bitwise_or, |);
OPAQUE_TYPE_ASSIGN_OPERATOR(exclusive_or, ^);

template <typename TDef>
struct numeric_arithmatic : unary_plus<TDef>, unary_minus<TDef>, addition<TDef>, subtraction<TDef>, multiplication<TDef>, division<TDef> {};

template <typename TDef>
struct integer_arithmatic : numeric_arithmatic<TDef>, modulo<TDef> {}

#undef OPAQUE_TYPE_BINARY_OPERATOR
#undef OPAQUE_TYPE_MIXED_BINARY_OPERATOR
#undef OPAQUE_TYPE_UNARY_OPERATOR
#undef OPAQUE_TYPE_ASSIGN_OPERATOR

template <typename Self, typename T>
class opaque_typedef {
public:
  opaque_typedef() : _value() {}
  explicit opaque_typedef(T const & val) : _value(val) {}
  explicit opaque_typedef(T && val) noexcept(std::is_nothrow_move_constructible<T>::value) : _value(std::move(val)) {}
  explicit operator T &() noexcept { return _value; }
  explicit operator T const&() const noexcept { return _value; }
  
  friend void swap(opaque_typedef & lhs, opaque_typedef & rhs) {
    using std::swap;
    swap(lhs._value, rhs._value);
  }
private:
  T _value;
};