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 #include #include #include #include #include #include typedef boost::fusion::vector Key; template typename boost::fusion::result_of::transform< boost::fusion::zip_view<SeqOfSeqs> const, boost::fusion::fused_function_object >::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(f)); } struct min { template <typename Sig> struct result; template 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<

I'm curious, wouldn't fusion's binary transform algorithm work for you? c = boost::fusion::transform(a, b, min());

Much simpler indeed! Thanks. Below is the full code. The part with struct result is a bit strange to me! I do not understand what Self(T, T) means. Frédéric #include <iostream> #include <string> #include #include #include #include typedef boost::fusion::vector Key; struct min { template <typename Sig> struct result; template 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<