A right heterogeneous fold on variadic tuples.

tuple_fold.cpp

#include <tuple>
#include <type_traits>
#include <utility>
#include <integer_sequence>

template <class F, class Tuple, size_t... I>
auto tuple_map_impl(F f, Tuple&& t, index_sequence<I...>)
{
    return std::make_tuple(f(std::get<I>(std::forward<Tuple>(t)))...);
}

template <class F, class Tuple, class... Tuples>
auto tuple_map(F f, Tuple&& t, Tuples&&... tuples)
{
    return std::tuple_cat(tuple_map_impl(f, std::forward<Tuple>(t),
                          std::make_index_sequence<std::tuple_size<std::decay_t<Tuple>>::value>{}),
                tuple_map(f, tuples...)
           );
}

template <class F>
auto tuple_map(F) { return std::make_tuple(); }