Element-wise tuple addition

Question

I have some values held in a tuple, and I am looking to add another tuple to it element-wise. So I would like functionality like this:

std::tuple         


        

Answer 1

You could use something like this, which supports all three of your syntax proposals:

#include 
#include 

namespace internal
{
    //see: https://stackoverflow.com/a/16387374/4181011
    template
    void add_rhs_to_lhs(T& t1, const T& t2, std::integer_sequence)
    {
        auto l = { (std::get(t1) += std::get(t2), 0)... };
        (void)l; // prevent unused warning
    }
}

template 
std::tuple& operator += (std::tuple& lhs, const std::tuple& rhs)
{
    internal::add_rhs_to_lhs(lhs, rhs, std::index_sequence_for{});
    return lhs;
}

template 
std::tuple operator + (std::tuple lhs, const std::tuple& rhs)
{
   return lhs += rhs;
}

Working example:

http://coliru.stacked-crooked.com/a/27b8cf370d44d3d5

http://coliru.stacked-crooked.com/a/ff24dae1c336b937

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I would still go with named structs in most cases. Tuples are seldom the correct choice.