From: David Abrahams (dave_at_[hidden])
Date: 2006-08-14 13:50:41
<imre_at_[hidden]> writes:
> Hi,
>
> Is it possible to do this trick during compilation time?
> I was able to go from type lists to boost::cons but I can't find a way to
> make that last step.
Not sure what you mean by "that last step..."
namespace mpl = boost::mpl;
using namespace mpl::placeholders;
typedef mpl::vector<int, long, char const*> types;
typedef mpl::fold<types, boost::cons<_2,_1> >::type tuple_type;
tuple_type some_tuple;
If you want it to be a specialization of the boost::tuple template
(misguided, IMO) you can do it, but not "algorithmically." You need a
bunch of partial specializations:
template <class V, std::size_t n = mpl::size<V>::type::value >
struct types_to_tuple;
template <class V>
struct types_to_tuple<V, 0>
{
typedef boost::tuple<> type;
}
template <class V>
struct types_to_tuple<V, 1>
{
typedef boost::tuple<typename mpl::at_n<0>::type> type;
}
template <class V>
struct types_to_tuple<V, 2>
{
typedef boost::tuple<typename mpl::at_n<0>::type, typename mpl::at_n<1>::type> type;
}
etc.
This works on mpl::vector. Getting it to work on mpl::list is
slightly more complicated.
-- Dave Abrahams Boost Consulting www.boost-consulting.com