ple</code>, <code>tie</code> and <code>get</code>. Further, <code>ref</code> and <code>cref</code> are defined directly under the <code>::boost</code> namespace.

<h2><a name = "tuple_types">Tuple types</a></h2>

<p>A tuple type is an instantiation of the <code>tuple</code> template. 
The template parameters specify the types of the tuple elements.
The current version supports tuples with 0-10 elements. 
If necessary, the upper limit can be increased up to, say, a few dozen elements.
The data element can be