Re: [Boost-users] [mpl] erase_key confusion

From: Gottlob Frege (gottlobfrege_at_[hidden])
Date: 2007-03-23 10:52:59

On 3/23/07, Scott Meyers <usenet_at_[hidden]> wrote:
>
> // return Seq with the first occurrance of T removed
> template<typename Seq, typename T>
> struct erase_first {
>    // i = Seq.find(T)
>    typedef typename mpl::find<Seq, T>::type i;
>
>    // found = (i == Seq.end()) ? false : true
>    typedef typename mpl::if_<
>      typename boost::is_same<i,
>                              typename mpl::end<Seq>::type
>                             >::type,
>      mpl::false_,
>      mpl::true_
>      >::type found;
>
>    // type = found ? Seq : Seq.erase(i)

// type = found ? Seq.erase(i) : Seq

>    typedef typename mpl::if_<found,
>                              Seq,
>                              typename mpl::erase<Seq, i>::type
>                          >::type type;

typedef typename if_<found,
                                typename mpl::erase<Seq, i>::type,
                                Seq
                              >::type type;

> };
>
> BOOST_MPL_ASSERT((
>    mpl::equal<
>      erase_first<set1, A>::type,
>      erase_first<set2, A>::type
>    >
> ));
>

Or did I misunderstand?

Tony