utl/include/utl/meta/basic.h

/*!
 * \file    utl/meta/basic.h
 * \brief   Template meta-programming basic definitions
 */
#ifndef __utl_meta_basic_h__
#define __utl_meta_basic_h__

#include <utl/core/impl.h>
#include <type_traits>
#include <utility>

/*!
 * \ingroup meta
 * \defgroup basic Basic
 * Basic definitions
 */
//! @{

/*!
 * \ingroup basic
 * \defgroup meta_core Core
 * Core definitions
 */
//! @{

namespace utl {
namespace meta {

   /*!
    * \brief   meta's empty type
    *
    * utl::meta's nil type is not pure nil. It's a recursive "de-referencable nil.
    * Each time someone applies \c \::type to it, he gets back nil_. This way we can prevent
    * a lot of compilation errors in a wrong meta:: handling.
    */
   struct nil_ {
      using type = nil_;
   };

   //! Type alias for \c Tp::type.
   //! Is used to evaluate/extract return type of metafunctions
   //! \tparam    Tp The metafunction to evaluate
   //! \return    The inner \::type
   template <typename Tp>
   using eval = typename Tp::type;

   //! Type alias for \c Tp::type::value.
   //! Is used to evaluate/extract return value of metafunctions
   //! \tparam    Tp The metafunction to evaluate
   //! \return    The inner \::type::value
   template <typename Tp>
   using eval_v = typename eval<Tp>::value;



   //!
   //! integral_ is a holder class for a compile-time value of an integral type.
   //!
   //! Every Integral Constant is also a null-ary Metafunction, returning itself.\n
   //! An integral constant object is implicitly convertible to the corresponding
   //! run-time value of the wrapped integral type
   template <typename Tp, Tp v>
   using integral_ = std::integral_constant<Tp, v>;


   //! \name Wrappers for basic types
   //! @{

   //! bool_ type: integral constant wrapper for bool
   template<bool v>
   using bool_ = integral_<bool, v>;

   using true_ = bool_<true>; //!< The type used as a compile-time boolean with true value.
   using false_ = bool_<false>; //!< The type used as a compile-time boolean with false value.

   //! int8_ type: integral constant wrapper for \c int8_t
   template<int8_t v>
   using int8_ = integral_<int8_t, v>;
   //! uint8_ type: integral constant wrapper for \c uint8_t
   template<uint8_t v>
   using uint8_ = integral_<uint8_t, v>;

   //! int16_ type: integral constant wrapper for \c int16_t
   template<int16_t v>
   using int16_ = integral_<int16_t, v>;
   //! uint16_ type: integral constant wrapper for \c uint16_t
   template<uint16_t v>
   using uint16_ = integral_<uint16_t, v>;

   //! int32_ type: integral constant wrapper for \c int32_t
   template<int32_t v>
   using int32_ = integral_<int32_t, v>;
   //! uint32_ type: integral constant wrapper for \c uint32_t
   template<uint32_t v>
   using uint32_ = integral_<uint32_t, v>;

   //! char_ type: integral constant wrapper for \c char
   template<char v>
   using char_ = integral_<char, v>;

   //! int_ type: integral constant wrapper for \c int
   template<int v>
   using int_ = integral_<int, v>;

   //! long_ type: integral constant wrapper for \c long
   template<long v>
   using long_ = integral_<long, v>;

   //! index_ type: integral constant wrapper for \c index_t a.k.a std::size_t
   template<index_t v>
   using index_ = integral_<index_t, v>;

   //! size_ type: integral constant wrapper for \c size_t a.k.a std::size_t
   template<size_t v>
   using size_ = integral_<size_t, v>;

   //! The last position we can express for indexing
   using Npos = size_<index_t(-1)>;
   //! @}

   //! \name unevaluated expressions
   //! @{

   //! Computes the size of the type \p Tp.
   //! Complexity \f$ O(1) \f$.
   template <typename Tp>
   using sizeof_ = size_<sizeof(Tp)>;

   //! Computes the alignment required for any instance of the type \p Tp.
   //! Complexity \f$ O(1) \f$.
   template <typename Tp>
   using alignof_ = size_<alignof(Tp)>;
   //! @}

   //! \name integer sequence
   //! @{
   template< class Tp, Tp... Ints >
   using integer_sequence = std::integer_sequence<Tp, Ints...>;

   template<typename Tp, Tp Num>
   using make_integer_sequence  = std::make_integer_sequence<Tp, Num>;

   //! Alias template index_sequence
   template<index_t... Idx>
   using index_sequence = integer_sequence<index_t, Idx...>;

   //! Alias template make_index_sequence
   template<index_t Num>
   using make_index_sequence = make_integer_sequence <index_t, Num>;

   //! Alias template index_sequence_for
   template<typename... Types>
   using index_sequence_for = make_index_sequence<sizeof...(Types)>;
   //! @}
}}

//!@}

/*!
 * \ingroup basic
 * \defgroup selection Selection
 * Type selection support header
 */
//! @{
namespace utl {
namespace meta{

   //! \name if implementation
   //! @{
   namespace details {
      template <bool If, typename...>
      struct if_c_ {
         using type = nil_;   //< avoid ill formed result
      };
      template<typename Then>
      struct if_c_<true, Then> {
         using type = Then;
      };
      template<typename Then, typename Else>
      struct if_c_<true, Then, Else> {
         using type = Then;
      };
      template<typename Then, typename Else>
      struct if_c_<false, Then, Else> {
         using type = Else;
      };
   }
   //! Select one type or another depending on a compile-time Boolean.
   template <bool B, typename... Args>
   using if_c = eval<details::if_c_<B, Args...>>;

   //! Select one type or another depending on a compile-time Boolean type
   template <typename If, typename... Args>
   using if_ = if_c<If::type::value, Args...>;
   //! @}

   /*!
    * \name Named type selectors
    */
   //! @{

   //! Select the first type of a type sequence
   template <typename T1, typename ...> using first_of = T1;

   //! Select the second type of a type sequence
   template <typename T1, typename T2, typename ...> using second_of = T2;
   //! @}
}}

//! @}



/*!
 * \ingroup basic
 * \defgroup logic_operations Logic Operations
 * logic operators and type relations support
 */
//! @{
namespace utl {
namespace meta{

   /*!
    * \name Logical relation for types
    */
   //! @{

   //! Negate the *bool* constant parameter and return bool_
   template <bool B>
   using not_c = bool_<!B>;

   //! negate the bool_ parameter and return bool_
   template<typename Tp>
   using not_ = not_c<Tp::type::value>;

   //! \name OR implementation
   //! @{
   namespace details {
      template<typename...> struct _or_;

      template<>
      struct _or_<> : false_ { };

      template<typename T1>
      struct _or_<T1> : T1 { };

      template<typename T1, typename T2>
      struct _or_ <T1, T2>
        : if_<T1, T1, T2> { };

      template<typename T1, typename T2, typename T3, typename... Tn>
      struct _or_<T1, T2, T3, Tn...>
         : if_<T1, T1, _or_<T2, T3, Tn...>> { };
   }

   //! Operator or for bool_ types
   //! \tparam Ts    Variadic args of type bool_
   //! \return Logical or as bool_
   template <typename... Ts>
   using or_ = eval<details::_or_<Ts...>>;
   //! @}

   //! \name AND implementation
   //! @{
   namespace details {
      template<typename...> struct _and_;

      template<>
      struct _and_<>
         : true_ { };

      template<typename T1>
      struct _and_ <T1>
         : T1 { };

      template<typename T1, typename T2>
      struct _and_<T1, T2>
         : if_<T1, T2, T1> { };

      template<typename T1, typename T2, typename T3, typename... Tn>
      struct _and_<T1, T2, T3, Tn...>
         : if_<T1, _and_<T2, T3, Tn...>, T1> { };
   }

   //! Operator and for bool_ types
   //! \tparam Ts    Variadic args of type bool_
   //! \return Logical and as bool_
   template <typename... Ts>
   using and_ = eval<details::_and_<Ts...>>;
   //! @}

   //! \name same
   //! @{
   template<typename T1, typename T2>
   struct same_ : false_ { };

   template<typename Tp>
   struct same_ <Tp, Tp> : true_ { };

   template<typename T1, typename T2>
   using not_same_ = not_<eval<same_<T1, T2>>>;
   //! @}

   //! @}
}}

//! @}


/*!
 * \ingroup basic
 * \defgroup integral_operators integral operators
 * Type arithmetic and operations
 */
//! @{

namespace utl {
namespace meta {

   /*!
    * \name Math operations
    */
   //! @{

   //! Negation
   template <typename Tp>
   using negate = integral_<decltype(-Tp()), -Tp()>;
   //! Addition
   template <typename Tp1, typename Tp2>
   using add = integral_<
                  decltype(Tp1() + Tp2()),
                  Tp1() + Tp2()
               >;
   //! Multiplication
   template <typename Tp1, typename Tp2>
   using mult = integral_<
                   decltype(Tp2() * Tp2()),
                   Tp1() * Tp2()
                >;
   //! Division
   template <typename Tp1, typename Tp2>
   using divide = integral_<
                     decltype(Tp2() / Tp2()),
                     Tp1() / Tp2()
                  >;
    //! Modulo
    template <typename Tp1, typename Tp2>
    using modulo = integral_<
                      decltype(Tp1() % Tp2()),
                      Tp1() % Tp2()
                   >;
   //! Substruction
   template <typename Tp1, typename Tp2>
   using sub = add<Tp1, negate<Tp2>>;

   //! Increase
   template <typename Tp>
   using inc = add<Tp, int_<1>>;

   //! decrease
   template <typename Tp>
   using dec = add<Tp, int_<-1>>;

   //! @}

   /*!
    * \name Comparison operations
    */
   //! @{

   //! \return a true-valued Integral Constant if Tp1 and Tp2 are equal.
   template <typename Tp1, typename Tp2>  using comp_eq = bool_<Tp1() == Tp2()>;
   //! \return a true-valued Integral Constant if Tp1 is less than Tp2.
   template <typename Tp1, typename Tp2>  using comp_lt = bool_<(Tp1() < Tp2())>;

   //! Not equal
   template <typename Tp1, typename Tp2>  using comp_ne = not_<comp_eq<Tp1, Tp2>>;
   //! Greater than
   template <typename Tp1, typename Tp2>  using comp_gt = comp_lt <Tp2, Tp1>;
   //! Less or equal
   template <typename Tp1, typename Tp2>  using comp_le = not_<comp_lt<Tp2, Tp1>>;
   //! Greater or equal
   template <typename Tp1, typename Tp2>  using comp_ge = not_<comp_lt<Tp1, Tp2>>;
  //! @}

   /*!
    * \name Bitwise operations
    */
   //! @{

   //! \return bitwise not (~) operation of its argument.
   template <typename T>  using bitnot_ = integral_<typename T::value_type, (typename T::value_type)(~T())>;
   //! \return bitwise and (&) operation of its arguments
   template <typename Tp1, typename Tp2>
   using bitand_ = integral_<decltype(Tp1() & Tp2()), Tp1() & Tp2()>;
   //! \return bitwise or (|) operation of its arguments.
   template <typename Tp1, typename Tp2>
   using bitor_ = integral_<decltype(Tp1() | Tp2()), Tp1() | Tp2()>;

   //! \return bitwise xor (^) operation of its arguments.
   template <typename Tp1, typename Tp2>
   using bitxor_ = integral_<decltype(Tp1() ^ Tp2()), Tp1() ^ Tp2()>;
   //! \return the result of bitwise shift left (<<) operation on Tp.
   template <typename Tp, typename shift>
   using shift_left = integral_<typename Tp::value_type, (typename Tp::value_type)(Tp() << shift())>;
   //! \return the result of bitwise shift right (>>) operation on Tp.
   template <typename Tp, typename shift>
   using shift_right = integral_<typename Tp::value_type, (typename Tp::value_type)(Tp() >> shift())>;
   //! @}
}}
//! @}

//! @}

#endif /* __utl_meta_basic_h__ */