libstdc++-v3/include/tr1/tuple

// class template tuple -*- C++ -*-

// Copyright (C) 2004-2025 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file tr1/tuple
*  This is a TR1 C++ Library header.
*/

// Chris Jefferson <chris@bubblescope.net>
// Variadic Templates support by Douglas Gregor <doug.gregor@gmail.com>

#ifndef _GLIBCXX_TR1_TUPLE
#define _GLIBCXX_TR1_TUPLE 1

#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wc++11-extensions"

#include <bits/requires_hosted.h> // TR1

#include <utility>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

namespace tr1
{
  // Adds a const reference to a non-reference type.
  template<typename _Tp>
    struct __add_c_ref
    { typedef const _Tp& type; };

  template<typename _Tp>
    struct __add_c_ref<_Tp&>
    { typedef _Tp& type; };

  // Adds a reference to a non-reference type.
  template<typename _Tp>
    struct __add_ref
    { typedef _Tp& type; };

  template<typename _Tp>
    struct __add_ref<_Tp&>
    { typedef _Tp& type; };

  /**
   * Contains the actual implementation of the @c tuple template, stored
   * as a recursive inheritance hierarchy from the first element (most
   * derived class) to the last (least derived class). The @c Idx
   * parameter gives the 0-based index of the element stored at this
   * point in the hierarchy; we use it to implement a constant-time
   * get() operation.
   */
  template<int _Idx, typename... _Elements>
    struct _Tuple_impl; 

  /**
   * Zero-element tuple implementation. This is the basis case for the 
   * inheritance recursion.
   */
  template<int _Idx>
    struct _Tuple_impl<_Idx> { };

  /**
   * Recursive tuple implementation. Here we store the @c Head element
   * and derive from a @c Tuple_impl containing the remaining elements
   * (which contains the @c Tail).
   */
  template<int _Idx, typename _Head, typename... _Tail>
    struct _Tuple_impl<_Idx, _Head, _Tail...>
    : public _Tuple_impl<_Idx + 1, _Tail...>
    {
      typedef _Tuple_impl<_Idx + 1, _Tail...> _Inherited;
      
      _Head _M_head;
      
      _Inherited&       _M_tail()       { return *this; }
      const _Inherited& _M_tail() const { return *this; }
      
      _Tuple_impl() : _Inherited(), _M_head() { }
      
      explicit 
      _Tuple_impl(typename __add_c_ref<_Head>::type __head,
		  typename __add_c_ref<_Tail>::type... __tail)
      : _Inherited(__tail...), _M_head(__head) { }

      template<typename... _UElements>
      _Tuple_impl(const _Tuple_impl<_Idx, _UElements...>& __in)
      : _Inherited(__in._M_tail()), _M_head(__in._M_head) { }

      _Tuple_impl(const _Tuple_impl& __in)
      : _Inherited(__in._M_tail()), _M_head(__in._M_head) { }
     
      template<typename... _UElements>
        _Tuple_impl&
        operator=(const _Tuple_impl<_Idx, _UElements...>& __in)
        {
	  _M_head = __in._M_head;
	  _M_tail() = __in._M_tail();
	  return *this;
	}

      _Tuple_impl&
      operator=(const _Tuple_impl& __in)
      {
	_M_head = __in._M_head;
	_M_tail() = __in._M_tail();
	return *this;
      }
    };

  template<typename... _Elements> 
    class tuple : public _Tuple_impl<0, _Elements...>
    {
      typedef _Tuple_impl<0, _Elements...> _Inherited;

    public:
      tuple() : _Inherited() { }

      explicit
      tuple(typename __add_c_ref<_Elements>::type... __elements)
      : _Inherited(__elements...) { }

      template<typename... _UElements>
        tuple(const tuple<_UElements...>& __in)
	: _Inherited(__in) { }

      tuple(const tuple& __in)
      : _Inherited(__in) { }

      template<typename... _UElements>
        tuple&
        operator=(const tuple<_UElements...>& __in)
        {
	  static_cast<_Inherited&>(*this) = __in;
	  return *this;
	}

      tuple&
      operator=(const tuple& __in)
      {
	static_cast<_Inherited&>(*this) = __in;
	return *this;
      }
    };

  template<> class tuple<> { };

  // 2-element tuple, with construction and assignment from a pair.
  template<typename _T1, typename _T2>
    class tuple<_T1, _T2> : public _Tuple_impl<0, _T1, _T2>
    {
      typedef _Tuple_impl<0, _T1, _T2> _Inherited;

    public:
      tuple() : _Inherited() { }

      explicit
      tuple(typename __add_c_ref<_T1>::type __a1,
	    typename __add_c_ref<_T2>::type __a2)
      : _Inherited(__a1, __a2) { }

      template<typename _U1, typename _U2>
        tuple(const tuple<_U1, _U2>& __in)
	: _Inherited(__in) { }

      tuple(const tuple& __in)
      : _Inherited(__in) { }

      template<typename _U1, typename _U2>
        tuple(const pair<_U1, _U2>& __in)
	: _Inherited(_Tuple_impl<0, 
		     typename __add_c_ref<_U1>::type,
		     typename __add_c_ref<_U2>::type>(__in.first, 
						      __in.second))
        { }
  
      template<typename _U1, typename _U2>
        tuple&
        operator=(const tuple<_U1, _U2>& __in)
        {
	  static_cast<_Inherited&>(*this) = __in;
	  return *this;
	}

      tuple&
      operator=(const tuple& __in)
      {
	static_cast<_Inherited&>(*this) = __in;
	return *this;
      }

      template<typename _U1, typename _U2>
        tuple&
        operator=(const pair<_U1, _U2>& __in)
        {
	  this->_M_head = __in.first;
	  this->_M_tail()._M_head = __in.second;
	  return *this;
	}
    };

  
  /// Gives the type of the ith element of a given tuple type.
  template<int __i, typename _Tp>
    struct tuple_element;

  /**
   * Recursive case for tuple_element: strip off the first element in
   * the tuple and retrieve the (i-1)th element of the remaining tuple.
   */
  template<int __i, typename _Head, typename... _Tail>
    struct tuple_element<__i, tuple<_Head, _Tail...> >
    : tuple_element<__i - 1, tuple<_Tail...> > { };

  /**
   * Basis case for tuple_element: The first element is the one we're seeking.
   */
  template<typename _Head, typename... _Tail>
    struct tuple_element<0, tuple<_Head, _Tail...> >
    {
      typedef _Head type;
    };

  /// Finds the size of a given tuple type.
  template<typename _Tp>
    struct tuple_size;

  /// class tuple_size
  template<typename... _Elements>
    struct tuple_size<tuple<_Elements...> >
    {
      static const int value = sizeof...(_Elements);
    };

  template<typename... _Elements>
    const int tuple_size<tuple<_Elements...> >::value;

  template<int __i, typename _Head, typename... _Tail>
    inline typename __add_ref<_Head>::type
    __get_helper(_Tuple_impl<__i, _Head, _Tail...>& __t)
    {
      return __t._M_head;
    }

  template<int __i, typename _Head, typename... _Tail>
    inline typename __add_c_ref<_Head>::type
    __get_helper(const _Tuple_impl<__i, _Head, _Tail...>& __t)
    {
      return __t._M_head;
    }

  // Return a reference (const reference) to the ith element of a tuple.
  // Any const or non-const ref elements are returned with their original type.
  template<int __i, typename... _Elements>
    inline typename __add_ref<
                      typename tuple_element<__i, tuple<_Elements...> >::type
                    >::type
    get(tuple<_Elements...>& __t)
    { 
      return __get_helper<__i>(__t); 
    }

  template<int __i, typename... _Elements>
    inline typename __add_c_ref<
                      typename tuple_element<__i, tuple<_Elements...> >::type
                    >::type
    get(const tuple<_Elements...>& __t)
    {
      return __get_helper<__i>(__t);
    }

  // This class helps construct the various comparison operations on tuples
  template<int __check_equal_size, int __i, int __j,
	   typename _Tp, typename _Up>
    struct __tuple_compare;

  template<int __i, int __j, typename _Tp, typename _Up>
    struct __tuple_compare<0, __i, __j, _Tp, _Up>
    {
      static bool __eq(const _Tp& __t, const _Up& __u)
      {
	return (get<__i>(__t) == get<__i>(__u) &&
		__tuple_compare<0, __i+1, __j, _Tp, _Up>::__eq(__t, __u));
      }
     
      static bool __less(const _Tp& __t, const _Up& __u)
      {
	return ((get<__i>(__t) < get<__i>(__u))
		|| !(get<__i>(__u) < get<__i>(__t)) &&
		__tuple_compare<0, __i+1, __j, _Tp, _Up>::__less(__t, __u));
      }
    };

  template<int __i, typename _Tp, typename _Up>
    struct __tuple_compare<0, __i, __i, _Tp, _Up>
    {
      static bool __eq(const _Tp&, const _Up&)
      { return true; }
     
      static bool __less(const _Tp&, const _Up&)
      { return false; }
    };

  template<typename... _TElements, typename... _UElements>
    bool
    operator==(const tuple<_TElements...>& __t,
	       const tuple<_UElements...>& __u)
    {
      typedef tuple<_TElements...> _Tp;
      typedef tuple<_UElements...> _Up;
      return (__tuple_compare<tuple_size<_Tp>::value - tuple_size<_Up>::value,
	      0, tuple_size<_Tp>::value, _Tp, _Up>::__eq(__t, __u));
    }

  template<typename... _TElements, typename... _UElements>
    bool
    operator<(const tuple<_TElements...>& __t,
	      const tuple<_UElements...>& __u)
    {
      typedef tuple<_TElements...> _Tp;
      typedef tuple<_UElements...> _Up;
      return (__tuple_compare<tuple_size<_Tp>::value - tuple_size<_Up>::value,
	      0, tuple_size<_Tp>::value, _Tp, _Up>::__less(__t, __u));
    }

  template<typename... _TElements, typename... _UElements>
    inline bool
    operator!=(const tuple<_TElements...>& __t,
	       const tuple<_UElements...>& __u)
    { return !(__t == __u); }

  template<typename... _TElements, typename... _UElements>
    inline bool
    operator>(const tuple<_TElements...>& __t,
	      const tuple<_UElements...>& __u)
    { return __u < __t; }

  template<typename... _TElements, typename... _UElements>
    inline bool
    operator<=(const tuple<_TElements...>& __t,
	       const tuple<_UElements...>& __u)
    { return !(__u < __t); }

  template<typename... _TElements, typename... _UElements>
    inline bool
    operator>=(const tuple<_TElements...>& __t,
	       const tuple<_UElements...>& __u)
    { return !(__t < __u); }

  template<typename _Tp>
    class reference_wrapper;

  // Helper which adds a reference to a type when given a reference_wrapper
  template<typename _Tp>
    struct __strip_reference_wrapper
    {
      typedef _Tp __type;
    };

  template<typename _Tp>
    struct __strip_reference_wrapper<reference_wrapper<_Tp> >
    {
      typedef _Tp& __type;
    };

  template<typename _Tp>
    struct __strip_reference_wrapper<const reference_wrapper<_Tp> >
    {
      typedef _Tp& __type;
    };

  template<typename... _Elements>
    inline tuple<typename __strip_reference_wrapper<_Elements>::__type...>
    make_tuple(_Elements... __args)
    {
      typedef tuple<typename __strip_reference_wrapper<_Elements>::__type...>
        __result_type;
      return __result_type(__args...);
    }

  template<typename... _Elements>
    inline tuple<_Elements&...>
    tie(_Elements&... __args)
    {
      return tuple<_Elements&...>(__args...);
    }

  // A class (and instance) which can be used in 'tie' when an element
  // of a tuple is not required
  struct _Swallow_assign
  {
    template<class _Tp>
      _Swallow_assign&
      operator=(const _Tp&)
      { return *this; }
  };

  // TODO: Put this in some kind of shared file.
  namespace
  {
    _Swallow_assign ignore  __attribute__((__unused__));
  } // anonymous namespace
}

_GLIBCXX_END_NAMESPACE_VERSION
}

#pragma GCC diagnostic pop
#endif // _GLIBCXX_TR1_TUPLE