Re: [boost] Oh exhalted MPL gurus...

From: Matthias Schabel (boost_at_[hidden])
Date: 2003-11-09 20:46:52

> Matthias Schabel wrote:
> >  How does one implement append? That is, given
> >
> >  typedef mpl::list<t1,t2,t3> l1;
> >  typedef mpl::list<t4,t5> l2;
> >
> >  typedef append<l1,l2> --> mpl::list<t1,t2,t3,t4,t5>
> >
> >  I've tried things like
> >
> >  typedef typename mpl::iter_fold<S2,S1,push_back<_1,deref<_2> >  
> >::type   a;
>
>    template<class Seq1, class Seq2>
>    struct append
>        : mpl::insert_range<
>             Seq1
>           , typename mpl::end<Seq1> ::type
>           , Seq2
>          >
>    {};
>
> --  
> Daniel Wallin

Should the following code compile?  I think so, based on your  
suggestion, but gcc 3.3 fails (I'm running on
Mac OS 10.3) at the static assert...

#include <boost/static_assert.hpp>
#include <boost/type_traits.hpp>

#include <boost/mpl/equal.hpp>
#include <boost/mpl/insert_range.hpp>
#include <boost/mpl/list.hpp>

struct t1 { };
struct t2 { };
struct t3 { };
struct t4 { };

template<class S1,class S2>
struct append :
        public boost::mpl::insert_range<S1,boost::mpl::end<S1>,S2>
{ };

int main()
{
        typedef boost::mpl::list<t1,t2,t3,t4>		l1;
        typedef boost::mpl::list<t4,t3,t2,t1>		l2;

        typedef append<l1,l2>::type	ap1;
        
        typedef boost::mpl::list<t1,t2,t3,t4,t4,t3,t2,t1>	l3;
        
        typedef boost::mpl::equal<ap1,l3>::type	b1;
        
        BOOST_STATIC_ASSERT((boost::is_same<b1,boost::mpl::true_>::value ==  
true));
                                  
        return 0;
}

------------------------------------------------------------------------ 
---------------------------
Matthias Schabel, Ph.D.                           	
Utah Center for Advanced Imaging Research
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mschabel at ucair med utah edu