Re: [Boost-users] mpl and mpl::vector_c and or_ and transform

Subject: Re: [Boost-users] mpl and mpl::vector_c and or_ and transform
From: Adam Merz (adammerz_at_[hidden])
Date: 2008-09-26 22:53:28

peter_foelsche wrote:
> This code does not compile.
> I'm using Visual C++.
> Any help would be appreciated.

I'm still quite unclear as to what you're trying to accomplish, but the
following compiles:

#include <utility>
#include <boost/mpl/placeholders.hpp>
#include <boost/mpl/back.hpp>
#include <boost/mpl/for_each.hpp>
#include <boost/mpl/front.hpp>
#include <boost/mpl/or.hpp>
#include <boost/mpl/transform.hpp>
#include <boost/mpl/vector.hpp>
#include <boost/mpl/zip_view.hpp>
#include <boost/noncopyable.hpp>

namespace mpl = boost::mpl;

template<typename T>
struct wrap { };

template<typename CDB>
struct CDer
{ };

template<typename CDB, typename CDB1>
struct CMyOperation : private boost::noncopyable
{
    typedef CDer
    <
        typename mpl::transform<CDB, CDB1, mpl::or_<mpl::_1, mpl::_2> >::type
    > CDerOr;

    CMyOperation(CDer<CDB> const& r0, CDer<CDB1> const& r1, CDerOr& rT)
    :   m_r0(r0),
        m_r1(r1),
        m_rT(rT),
        m_iPos(0)
    { }

    void operator ()(std::pair<bool, bool> const&)
    {
        ++m_iPos;
    }

private:
    CDer<CDB> const& m_r0;
    CDer<CDB1> const& m_r1;
    CDerOr& m_rT;
    unsigned m_iPos;
};

template<typename CDB, typename CDB1>
struct CCreatePair
{
    CCreatePair(CMyOperation<CDB, CDB1>& op) : m_sOp(&op) { }

    typedef void result_type;

    template<typename T>
    void operator ()(wrap<T>) const
    {
        typedef typename mpl::front<T>::type first;
        typedef typename mpl::back<T>::type second;

        (*m_sOp)(std::make_pair(first::value, second::value));
    }

private:
    CMyOperation<CDB, CDB1>* m_sOp;
};

template<typename CDB, typename CDB1>
typename CMyOperation<CDB, CDB1>::CDerOr myOperation(CDer<CDB> const& _r0,
                                                     CDer<CDB1> const& _r1)
{
    typedef mpl::zip_view<mpl::vector<CDB, CDB1> > CMerged;

    typename CMyOperation<CDB, CDB1>::CDerOr sRet;
    CMyOperation<CDB, CDB1> sOp(_r0, _r1, sRet);
    CCreatePair<CDB, CDB1> createPair(sOp);
    mpl::for_each<CMerged, wrap<mpl::_1> >(createPair);
    return sRet;
}

int main()
{
    CDer<mpl::vector<mpl::true_, mpl::true_> > sDer0;
    CDer<mpl::vector<mpl::false_, mpl::true_> > sDer1;

    myOperation(sDer0, sDer1);

    return 0;
}