Re: [Boost-users] [mpl] Please help with mpl::equal

From: Andy Little (andy_at_[hidden])
Date: 2006-04-21 06:42:50

"rincewind" wrote
> Please tell me why the following fragment prints 0 - I thought it should
> print 1:
>
>     typedef mpl::vector_c<int, 1, 2, 3> v1;
>     typedef mpl::vector<mpl::int_<1>, mpl::int_<2>, mpl::int_<3> > v2;
>     cout << mpl::equal<v1, v2>::value << "\n";

look in the definition of mpl equal <boost/mpl/equal.hpp> and you should be able
to discern the reason:

template<
      typename BOOST_MPL_AUX_NA_PARAM(Sequence1)
    , typename BOOST_MPL_AUX_NA_PARAM(Sequence2)
    , typename Predicate = is_same<_,_>
    >
struct equal;

Hint : Try changing the predicate to mpl::equal_to

regards
Andy Little