How is std::tuple implemented?

Question

I\'d like to know how are tuple implemented in standard library for C++0x. I tried to read description in libstdc++ manual and then read template listing, but it\'s really hard

Answer 1

I thought I would add a non-pseudocode simple recursive implementation for reference

#include 

// Contains the actual value for one item in the tuple. The 
// template parameter `i` allows the
// `Get` function to find the value in O(1) time
template
struct TupleLeaf {
    Item value;
};

// TupleImpl is a proxy for the final class that has an extra 
// template parameter `i`.
template
struct TupleImpl;

// Base case: empty tuple
template
struct TupleImpl{};

// Recursive specialization
template
struct TupleImpl :
    public TupleLeaf, // This adds a `value` member of type HeadItem
    public TupleImpl // This recurses
    {};

// Obtain a reference to i-th item in a tuple
template
HeadItem& Get(TupleImpl& tuple) {
    // Fully qualified name for the member, to find the right one 
    // (they are all called `value`).
    return tuple.TupleLeaf::value;
}

// Templated alias to avoid having to specify `i = 0`
template
using Tuple = TupleImpl<0, Items...>;

int main(int argc, char** argv) {
    Tuple tuple;
    Get<0>(tuple) = 5;
    Get<1>(tuple) = 8.3;
    Get<2>(tuple) = "Foo";
    std::cout << Get<0>(tuple) << std::endl;
    std::cout << Get<1>(tuple) << std::endl;
    std::cout << Get<2>(tuple) << std::endl;
    return 0;
}