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

One approach to implementing tuples is using multiple-inheritance. The tuple-elements are held by leaf-classes, and the tuple class itself inherits from multiple leafs. In pseudo-code:

template
class PseudoTuple : TupleLeaf<0, T0>, TupleLeaf<1, T1>, ..., TupleLeaf {
   ...
};

Each leaf has an index, so that each base-class becomes unique even if the types they contain are identical, so we can access the nth element with a simple static_cast:

static_cast*>(this);
// ...
static_cast*>(this);

I've written up a detailed explanation about this "flat" tuple implementation here: C++11 tuple implementation details (Part 1)