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

A tuple is typically implemented as a compile time linked-list.

The code is a bit obfuscated through template-syntax, but following elements are normally present:

1. a chain of classes with head and tail elements (cons-elements)
2. an empty tail instance to indicate the end of the list.
3. recursive code to walk the list to a certain index, implemented as recursive template-instantiations (instantiated at compile time).

There exist reasonable implementations in C++03 (e.g. boost).

Variadic templates allow an unlimited number of elements, as mentioned by Motti.

The cost is normally a compile time-one. Copy constructors might be called during initialization (max 1), and when copying the tuples themselves.