ly requires that the Buffer be updatable.

<p>Implicit in the definition is an ordering of values. Though access to the order is not required, types that model UpdatableQueue must document how an object of the type orders values so that a program may change the position of a given value in the ordering. For example, an UpdatableQueue may choose to order values by using a property map, and a value <tt>v1</tt> is considered less than a value <tt>v2</tt> if <tt><nobr>get(pm, v1) &lt; get(pm, v2)</nobr></tt>. A