Re: [Boost-users] [fusion] how to get the tuple of min values of 2 tuples whatever their length?

Subject: Re: [Boost-users] [fusion] how to get the tuple of min values of 2 tuples whatever their length?
From: Jeff Flinn (Jeffrey.Flinn_at_[hidden])
Date: 2013-07-18 07:23:09

On 7/18/2013 4:12 AM, Frédéric Bron wrote:
> Thank you all!
> It works now with the code below.
> What was the most difficult was to find the headers to include.
> Frédéric
>
> #include <iostream>
> #include <string>
>
> #include <boost/fusion/functional/adapter/fused_function_object.hpp>
> #include <boost/fusion/include/for_each.hpp>
> #include <boost/fusion/include/sequence.hpp>
> #include <boost/fusion/include/transform.hpp>
> #include <boost/fusion/include/vector_tie.hpp>
> #include <boost/fusion/include/zip_view.hpp>
> #include <boost/type_traits/remove_reference.hpp>
>
> typedef boost::fusion::vector<double, int, std::string, char> Key;
>
> template<class SeqOfSeqs, class Func>
> typename boost::fusion::result_of::transform<
> boost::fusion::zip_view<SeqOfSeqs> const,
> boost::fusion::fused_function_object<Func const &> >::type
> n_ary_transform(const SeqOfSeqs &s, const Func &f) {
>      return boost::fusion::transform(
>              boost::fusion::zip_view<SeqOfSeqs>(s),
>              boost::fusion::fused_function_object<const Func&>(f));
> }
>
> struct min {
>      template <typename Sig>
>      struct result;
>
>      template <class Self, typename T>
>      struct result< Self(T, T) > {
>          typedef typename boost::remove_reference<T>::type type;
>      };
>
>      template<typename T>
>      T operator()(const T &lhs, const T &rhs) const {
>          return std::min(lhs, rhs);
>      }
> };
>
> struct print {
>      template <class T>
>      void operator()(const T &rhs) const {
>          std::cout<<rhs<<'\n';
>      }
> };
>
> int main() {
>      Key a(1., 0, "zz", 'a');
>      Key b(2., -1, "aa", 'a');
>      Key c;
>      c=n_ary_transform(boost::fusion::vector_tie(a, b), min());
>      boost::fusion::for_each(c, print());
>      return 0;
> }
>

I'm curious, wouldn't fusion's binary transform algorithm work for you?

c = boost::fusion::transform(a, b, min());

Jeff