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/*=============================================================================
Copyright (c) 2001-2011 Joel de Guzman
Copyright (c) 2011 Nathan Ridge
Copyright (c) 2006 Dan Marsden
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)
==============================================================================*/
/*=============================================================================
An implementation of a std::pair like triple<T0, T1, T2>
We use fusion::sequence_facade and fusion::iterator_facade
to make our triple a fully conforming Boost.Fusion random
traversal sequence.
==============================================================================*/
#include <boost/detail/lightweight_test.hpp>
#include <boost/fusion/sequence/sequence_facade.hpp>
#include <boost/fusion/iterator/iterator_facade.hpp>
#include <boost/fusion/sequence/intrinsic.hpp>
#include <boost/fusion/iterator.hpp>
#include <boost/fusion/support/category_of.hpp>
#include <boost/fusion/algorithm/iteration/fold.hpp>
#include <boost/mpl/int.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/mpl/minus.hpp>
#include <boost/mpl/assert.hpp>
#include <boost/type_traits/is_const.hpp>
#include <boost/type_traits/is_same.hpp>
#include <string>
namespace mpl = boost::mpl;
namespace fusion = boost::fusion;
namespace demo
{
template<typename Seq, int N>
struct triple_iterator
: fusion::iterator_facade<triple_iterator<Seq, N>,
fusion::random_access_traversal_tag>
{
typedef mpl::int_<N> index;
typedef Seq sequence_type;
triple_iterator(Seq& seq)
: seq_(seq) {}
Seq& seq_;
template<typename T>
struct value_of;
template<typename Sq>
struct value_of<triple_iterator<Sq, 0> >
: mpl::identity<typename Sq::t0_type>
{};
template<typename Sq>
struct value_of<triple_iterator<Sq, 1> >
: mpl::identity<typename Sq::t1_type>
{};
template<typename Sq>
struct value_of<triple_iterator<Sq, 2> >
: mpl::identity<typename Sq::t2_type>
{};
template<typename T>
struct deref;
template <typename Sq>
struct deref<triple_iterator<Sq, 0> >
{
typedef typename Sq::t0_type& type;
static type
call(triple_iterator<Sq, 0> const& iter)
{
return iter.seq_.t0;
}
};
template <typename Sq>
struct deref<triple_iterator<Sq, 0> const>
{
typedef typename Sq::t0_type const& type;
static type
call(triple_iterator<Sq, 0> const& iter)
{
return iter.seq_.t0;
}
};
template <typename Sq>
struct deref<triple_iterator<Sq, 1> >
{
typedef typename Sq::t1_type& type;
static type
call(triple_iterator<Sq, 1> const& iter)
{
return iter.seq_.t1;
}
};
template <typename Sq>
struct deref<triple_iterator<Sq, 1> const>
{
typedef typename Sq::t1_type const& type;
static type
call(triple_iterator<Sq, 1> const& iter)
{
return iter.seq_.t1;
}
};
template <typename Sq>
struct deref<triple_iterator<Sq, 2> >
{
typedef typename Sq::t2_type& type;
static type
call(triple_iterator<Sq, 2> const& iter)
{
return iter.seq_.t2;
}
};
template <typename Sq>
struct deref<triple_iterator<Sq, 2> const>
{
typedef typename Sq::t2_type const& type;
static type
call(triple_iterator<Sq, 2> const& iter)
{
return iter.seq_.t2;
}
};
template<typename It>
struct next
{
typedef triple_iterator<
typename It::sequence_type, It::index::value + 1>
type;
static type call(It const& it)
{
return type(it.seq_);
}
};
template<typename It>
struct prior
{
typedef triple_iterator<
typename It::sequence_type, It::index::value - 1>
type;
static type call(It const& it)
{
return type(it.seq_);
}
};
template<typename It1, typename It2>
struct distance
{
typedef typename mpl::minus<
typename It2::index, typename It1::index>::type
type;
static type call(It1 const& it1, It2 const& it2)
{
return type();
}
};
template<typename It, typename M>
struct advance
{
typedef triple_iterator<
typename It::sequence_type,
It::index::value + M::value>
type;
static type call(It const& it)
{
return type(it.seq_);
}
};
};
template<typename T0, typename T1, typename T2>
struct triple
: fusion::sequence_facade<triple<T0, T1, T2>,
fusion::random_access_traversal_tag>
{
triple(T0 const& t0, T1 const& t1, T2 const& t2)
: t0(t0), t1(t1), t2(t2)
{}
template<typename Sq>
struct begin
{
typedef demo::triple_iterator<Sq, 0> type;
static type call(Sq& sq)
{
return type(sq);
}
};
template<typename Sq>
struct end
{
typedef demo::triple_iterator<Sq, 3> type;
static type call(Sq& sq)
{
return type(sq);
}
};
template<typename Sq>
struct size
: mpl::int_<3>
{};
template<typename Sq, typename N>
struct value_at
: value_at<Sq, mpl::int_<N::value> >
{};
template<typename Sq>
struct value_at<Sq, mpl::int_<0> >
{
typedef typename Sq::t0_type type;
};
template<typename Sq>
struct value_at<Sq, mpl::int_<1> >
{
typedef typename Sq::t1_type type;
};
template<typename Sq>
struct value_at<Sq, mpl::int_<2> >
{
typedef typename Sq::t2_type type;
};
template<typename Sq, typename N>
struct at
: at<Sq, mpl::int_<N::value> >
{};
template<typename Sq>
struct at<Sq, mpl::int_<0> >
{
typedef typename
mpl::if_<
boost::is_const<Sq>
, typename Sq::t0_type const&
, typename Sq::t0_type&
>::type
type;
static type call(Sq& sq)
{
return sq.t0;
}
};
template<typename Sq>
struct at<Sq, mpl::int_<1> >
{
typedef typename
mpl::if_<
boost::is_const<Sq>
, typename Sq::t1_type const&
, typename Sq::t1_type&
>::type
type;
static type call(Sq& sq)
{
return sq.t1;
}
};
template<typename Sq>
struct at<Sq, mpl::int_<2> >
{
typedef typename
mpl::if_<
boost::is_const<Sq>
, typename Sq::t2_type const&
, typename Sq::t2_type&
>::type
type;
static type call(Sq& sq)
{
return sq.t2;
}
};
typedef T0 t0_type;
typedef T1 t1_type;
typedef T2 t2_type;
T0 t0;
T1 t1;
T2 t2;
};
}
struct modifying_fold_functor
{
template <typename T>
struct result
{
typedef bool type;
};
template <typename T>
bool operator()(bool b, T&)
{
return b;
}
};
struct nonmodifying_fold_functor
{
template <typename T>
struct result
{
typedef bool type;
};
template <typename T>
bool operator()(bool b, const T&)
{
return b;
}
};
int main()
{
typedef demo::triple<int, char, std::string> my_triple;
my_triple t(101, 'a', "hello");
BOOST_TEST(*fusion::begin(t) == 101);
BOOST_TEST(*fusion::next(fusion::begin(t)) == 'a');
BOOST_TEST(*fusion::prior(fusion::end(t)) == "hello");
BOOST_TEST(fusion::distance(fusion::begin(t), fusion::end(t)) == 3);
BOOST_TEST(fusion::size(t) == 3);
BOOST_MPL_ASSERT((boost::is_same<
int, fusion::result_of::value_at_c<my_triple, 0>::type>));
BOOST_MPL_ASSERT((boost::is_same<
char, fusion::result_of::value_at_c<my_triple, 1>::type>));
BOOST_MPL_ASSERT((boost::is_same<
std::string, fusion::result_of::value_at_c<my_triple, 2>::type>));
BOOST_TEST(fusion::at_c<0>(t) == 101);
BOOST_TEST(fusion::at_c<1>(t) == 'a');
BOOST_TEST(fusion::at_c<2>(t) == "hello");
BOOST_TEST(fusion::fold(t, true, modifying_fold_functor()) == true);
BOOST_TEST(fusion::fold(t, true, nonmodifying_fold_functor()) == true);
return boost::report_errors();
}
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