Re: [boost] MPL - mpl::sequence to std::sequence

From: Terje Slettebø (tslettebo_at_[hidden])
Date: 2004-10-09 21:28:37

>From: "Jaap Suter" <boost_at_[hidden]>

> what is the easiest way to convert an mpl::sequence to an std::sequence?
>
> I'm using such conversions a lot when unit-testing meta-code. I just wrote
> two versions of algorithms, a compile-time and the runtime one, and then
> compare their outputs.
>
> I recall hearing something about mpl::for_each having defined an operator
()
> for runtime purposes, but the details don't seem to be documented
anywhere.

Yeah, I guess Aleksey and Dave have been busy with the forthcoming MPL book,
but as I understand from list postings, the MPL docs will be updated in
Boost 1.32, and mpl::for_each is one of the more useful components. Since
it's not documented, I learned how it works from Aleksey. The following
works with your code:

template<class T>
struct to_sequence
{
public:
  to_sequence(T &s) : sequence(s) {}

  template<class Element>
  void operator()(Element e)
  {
    sequence.push_back(e.value);
  }

private:
  T &sequence;
};

...

//    int_vector r_list = to_runtime<c_list>();

    int_vector r_list;

    boost::mpl::for_each<c_list>(to_sequence<int_vector>(r_list));

Regards,

Terje