Re: [Boost-users] Boost.MPL.Vector -> Boost.Tuple

Subject: Re: [Boost-users] Boost.MPL.Vector -> Boost.Tuple
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-09-05 15:11:12

AMDG

???? ????? wrote:
> typedef boost::mpl::vector< A, B, C > Sequence;
>
> typedef typename Question< Sequence >::type Result;
>
> BOOST_MPL_ASSERT( boost::mpl::is_same< Result, boost::tuple< A, B, C > >);
> How write Question? I don't want to write specialisation for every dimension
> of tuple manually.
> Implementation should be compatible with the last stable Boost release
> (1.36)
> Thank you
>   

#include <boost/tuple/tuple.hpp>
#include <boost/mpl/vector.hpp>
#include <boost/mpl/copy.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/preprocessor/repetition/enum_params.hpp>

struct A {};
struct B {};
struct C {};

typedef boost::mpl::vector< A, B, C > Sequence;

template<class T, class Tuple>
struct tuple_push_front;

template<class T, BOOST_PP_ENUM_PARAMS(10, class T)>
struct tuple_push_front<T, boost::tuple<BOOST_PP_ENUM_PARAMS(10, T)> > {
typedef boost::tuple<T, BOOST_PP_ENUM_PARAMS(9, T)> type;
};

template<class Sequence>
struct Question {
typedef typename boost::mpl::reverse_copy<
Sequence, boost::mpl::inserter<boost::tuple<>,
tuple_push_front<boost::mpl::_2, boost::mpl::_1> >
 >::type type;
};

typedef Question< Sequence >::type Result;
BOOST_MPL_ASSERT((boost::is_same< Result, boost::tuple< A, B, C > >));

In Christ,
Steven Watanabe