C++0x: How can I access variadic tuple members by index at runtime?

Question

I have written the following basic Tuple template:

template 
class Tuple;

template 
struct TupleIndex         


        

Answer 1

You do the exact same thing as you do with TupleIndexer, just at runtime.

Add a function like this to the Tuple class:

Head &operator[](unsigned i) {
    return i ? ((Tuple&)*this)[i-1] : element;
}

and add a specialization for Tuple:

Head &operator[](unsigned i) {
    assert(!i);
    return i;
}

(You can't put the base case into Tuple<>, since you don't have a type to return that would be compatible with every possible caller.)