C++ Tuple vs Struct

Question

Is there is any difference between using a std::tuple and a data-only struct?

typedef std::tuple foo_t;

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Answer 1

As far as the "generic function" go, Boost.Fusion deserves some love... and especially BOOST_FUSION_ADAPT_STRUCT.

Ripping from the page: ABRACADBRA

namespace demo
{
    struct employee
    {
        std::string name;
        int age;
    };
}

// demo::employee is now a Fusion sequence
BOOST_FUSION_ADAPT_STRUCT(
    demo::employee
    (std::string, name)
    (int, age))

This means that all Fusion algorithms are now applicable to the struct demo::employee.

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EDIT: Regarding the performance difference or layout compatibility, tuple's layout is implementation defined so not compatible (and thus you should not cast between either representation) and in general I would expect no difference performance-wise (at least in Release) thanks to the inlining of get.