tuple_basic_no_partial_spec.hpp

C++的一个好库。。。现在很流行

// - tuple_basic_no_partial_spec.hpp -----------------------------------------

// Copyright (C) 1999, 2000 Jaakko J鋜vi ([e-mail])
// Copyright (C) 2001 Douglas Gregor ([e-mail])
// Copyright (C) 2001 Gary Powell ([e-mail])
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

// For more information, see http://www.boost.org or http://lambda.cs.utu.fi

// Revision History
//  14 02 01    Remove extra ';'. Also, fixed 10-parameter to make_tuple. (DG)
//  10 02 01    Fixed "null_type" constructors.
//              Implemented comparison operators globally.
//              Hide element_type_ref and element_type_const_ref.
//              (DG).
//  09 02 01    Extended to tuples of length 10. Changed comparison for
//              operator<()
//              to the same used by std::pair<>, added cnull_type() (GP)
//  03 02 01    Initial Version from original tuple.hpp code by JJ. (DG)

// -----------------------------------------------------------------

#ifndef BOOST_TUPLE_BASIC_NO_PARTIAL_SPEC_HPP
#define BOOST_TUPLE_BASIC_NO_PARTIAL_SPEC_HPP

#include "boost/type_traits.hpp"
#include <utility>

#if defined BOOST_MSVC
#pragma warning(disable:4518) // storage-class or type specifier(s) unexpected here; ignored
#pragma warning(disable:4181) // qualifier applied to reference type ignored
#pragma warning(disable:4227) // qualifier applied to reference type ignored
#endif

namespace boost {
namespace tuples {

    // null_type denotes the end of a list built with "cons"
    struct null_type
    {
      null_type() {}
      null_type(const null_type&, const null_type&) {}
    };

    // a helper function to provide a const null_type type temporary
    inline const null_type cnull_type() { return null_type(); }

// forward declaration of tuple
    template<
      typename T1 = null_type,
      typename T2 = null_type,
      typename T3 = null_type,
      typename T4 = null_type,
      typename T5 = null_type,
      typename T6 = null_type,
      typename T7 = null_type,
      typename T8 = null_type,
      typename T9 = null_type,
      typename T10 = null_type
    >
    class tuple;

// forward declaration of cons
    template<typename Head, typename Tail = null_type>
    struct cons;

    namespace detail {

      // Takes a pointer and routes all assignments to whatever it points to
      template<typename T>
      struct assign_to_pointee
      {
      public:
        explicit assign_to_pointee(T* p) : ptr(p) {}

        template<typename Other>
        assign_to_pointee& operator=(const Other& other)
        {
          *ptr = other;
          return *this;
        }

      private:
        T* ptr;
      };

      // Swallows any assignment
      struct swallow_assign
      {
        template<typename T>
        swallow_assign const& operator=(const T&) const
        {
          return *this;
        }
      };

    template <typename T> struct add_const_reference : add_reference<typename add_const<T>::type> {};

    template <class MyTail>
    struct init_tail
    {
        // Each of vc6 and vc7 seem to require a different formulation
        // of this return type
        template <class H, class T>
#if BOOST_WORKAROUND(BOOST_MSVC, == 1200)
        static typename add_reference<typename add_const<T>::type>::type
#else
        static typename add_const_reference<T>::type
#endif
        execute( cons<H,T> const& u, long )
        {
            return u.get_tail();
        }
    };

    template <>
    struct init_tail<null_type>
    {
        template <class H>
        static null_type execute( cons<H,null_type> const& u, long )
        {
            return null_type();
        }

        template <class U>
        static null_type execute(U const&, ...)
        {
            return null_type();
        }
     private:
        template <class H, class T>
        void execute( cons<H,T> const&, int);
    };

    template <class Other>
    Other const&
    init_head( Other const& u, ... )
    {
        return u;
    }

    template <class H, class T>
    typename add_reference<typename add_const<H>::type>::type
    init_head( cons<H,T> const& u, int )
    {
        return u.get_head();
    }

    inline char**** init_head(null_type const&, int);

  } // end of namespace detail

    // cons builds a heterogenous list of types
   template<typename Head, typename Tail>
   struct cons
   {
     typedef cons self_type;
     typedef Head head_type;
     typedef Tail tail_type;

    private:
       typedef typename boost::add_reference<head_type>::type head_ref;
       typedef typename boost::add_reference<tail_type>::type tail_ref;
       typedef typename detail::add_const_reference<head_type>::type head_cref;
       typedef typename detail::add_const_reference<tail_type>::type tail_cref;
    public:
     head_type head;
     tail_type tail;

     head_ref get_head() { return head; }
     tail_ref get_tail() { return tail; }

     head_cref get_head() const { return head; }
     tail_cref get_tail() const { return tail; }

     cons() : head(), tail() {}

#if defined BOOST_MSVC
      template<typename Tail>
      cons(head_cref h /* = head_type() */, // causes MSVC 6.5 to barf.
                    const Tail& t) : head(h), tail(t.head, t.tail)
      {
      }

      cons(head_cref h /* = head_type() */, // causes MSVC 6.5 to barf.
                    const null_type& t) : head(h), tail(t)
      {
      }

#else
      template<typename T>
      explicit cons(head_cref h, const T& t) :
        head(h), tail(t.head, t.tail)
      {
      }

      explicit cons(head_cref h = head_type(),
                    tail_cref t = tail_type()) :
        head(h), tail(t)
      {
      }
#endif

      template <class U>
      cons( const U& u )
        : head(detail::init_head(u, 0))
        , tail(detail::init_tail<Tail>::execute(u, 0L))
       {
       }

      template<typename Other>
      cons& operator=(const Other& other)
      {
        head = other.head;
        tail = other.tail;
        return *this;
      }
    };

    namespace detail {

      // Determines if the parameter is null_type
      template<typename T> struct is_null_type { enum { RET = 0 }; };
      template<> struct is_null_type<null_type> { enum { RET = 1 }; };

      /* Build a cons structure from the given Head and Tail. If both are null_type,
      return null_type. */
      template<typename Head, typename Tail>
      struct build_cons
      {
      private:
        enum { tail_is_null_type = is_null_type<Tail>::RET };
      public:
        typedef cons<Head, Tail> RET;
      };

      template<>
      struct build_cons<null_type, null_type>
      {
        typedef null_type RET;
      };

      // Map the N elements of a tuple into a cons list
      template<
        typename T1,
        typename T2 = null_type,
        typename T3 = null_type,
        typename T4 = null_type,
        typename T5 = null_type,
        typename T6 = null_type,
        typename T7 = null_type,
        typename T8 = null_type,
        typename T9 = null_type,
        typename T10 = null_type
      >
      struct map_tuple_to_cons
      {
        typedef typename detail::build_cons<T10, null_type  >::RET cons10;
        typedef typename detail::build_cons<T9, cons10>::RET cons9;
        typedef typename detail::build_cons<T8, cons9>::RET cons8;
        typedef typename detail::build_cons<T7, cons8>::RET cons7;
        typedef typename detail::build_cons<T6, cons7>::RET cons6;
        typedef typename detail::build_cons<T5, cons6>::RET cons5;
        typedef typename detail::build_cons<T4, cons5>::RET cons4;
        typedef typename detail::build_cons<T3, cons4>::RET cons3;
        typedef typename detail::build_cons<T2, cons3>::RET cons2;
        typedef typename detail::build_cons<T1, cons2>::RET cons1;
      };

      // Workaround the lack of partial specialization in some compilers
      template<int N>
      struct _element_type
      {
        template<typename Tuple>
        struct inner
        {
        private:
          typedef typename Tuple::tail_type tail_type;
          typedef _element_type<N-1> next_elt_type;

        public:
          typedef typename _element_type<N-1>::template inner<tail_type>::RET RET;
        };
      };

      template<>
      struct _element_type<0>
      {
        template<typename Tuple>
        struct inner
        {
          typedef typename Tuple::head_type RET;
        };
      };

    } // namespace detail


    // Return the Nth type of the given Tuple
    template<int N, typename Tuple>
    struct element
    {
    private:
      typedef detail::_element_type<N> nth_type;

    public:
      typedef typename nth_type::template inner<Tuple>::RET RET;
      typedef RET type;
    };

    namespace detail {

#if defined(BOOST_MSVC) && (BOOST_MSVC == 1300)
      // special workaround for vc7:

      template <bool x>
      struct reference_adder
      {
         template <class T>
         struct rebind
         {
            typedef T& type;
         };
      };

      template <>
      struct reference_adder<true>
      {
         template <class T>
         struct rebind
         {
            typedef T type;
         };
      };


      // Return a reference to the Nth type of the given Tuple
      template<int N, typename Tuple>
      struct element_ref
      {
      private:
         typedef typename element<N, Tuple>::RET elt_type;
         enum { is_ref = is_reference<elt_type>::value };

      public:
         typedef reference_adder<is_ref>::rebind<elt_type>::type RET;
         typedef RET type;
      };

      // Return a const reference to the Nth type of the given Tuple
      template<int N, typename Tuple>
      struct element_const_ref
      {
      private:
         typedef typename element<N, Tuple>::RET elt_type;
         enum { is_ref = is_reference<elt_type>::value };

      public:
         typedef reference_adder<is_ref>::rebind<const elt_type>::type RET;
         typedef RET type;
      };

#else // vc7

      // Return a reference to the Nth type of the given Tuple
      template<int N, typename Tuple>
      struct element_ref
      {
      private:
        typedef typename element<N, Tuple>::RET elt_type;

      public:
        typedef typename add_reference<elt_type>::type RET;
        typedef RET type;
      };

      // Return a const reference to the Nth type of the given Tuple
      template<int N, typename Tuple>
      struct element_const_ref
      {
      private:
        typedef typename element<N, Tuple>::RET elt_type;

      public:
        typedef typename add_reference<const elt_type>::type RET;
        typedef RET type;
      };
#endif // vc7

    } // namespace detail

    // Get length of this tuple
    template<typename Tuple>
    struct length
    {
      BOOST_STATIC_CONSTANT(int, value = 1 + length<typename Tuple::tail_type>::value);
    };

    template<> struct length<tuple<> > {
      BOOST_STATIC_CONSTANT(int, value = 0);
    };

    template<>
    struct length<null_type>
    {
      BOOST_STATIC_CONSTANT(int, value = 0);
    };

    namespace detail {

    // Reference the Nth element in a tuple and retrieve it with "get"
    template<int N>
    struct get_class
    {
      template<typename Head, typename Tail>
      static inline
      typename detail::element_ref<N, cons<Head, Tail> >::RET
      get(cons<Head, Tail>& t)