UpdatableQueue
An UpdatableQueue is a refinement of the Buffer concept that additionally requires that the Buffer be updatable.
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 v1 is considered less than a value v2 if
get(pm, v1) < get(pm, v2). A program can update the properties of
values, thus changing the order of values in the UpdatableQueue, and
notify the UpdatableQueue of the specific values that have a different
position in the ordering by calling the update member of the
UpdatableQueue on each.
A program that modifies the order must notify the UpdatableQueue of values that may have different positions in the ordering since they were inserted or last updated.
Members
For a type to model the UpdatableQueue concept it must have the following members in addition to the members that are required of types that model Buffer:
| Member | Description |
|---|---|
|
Informs
the UpdatableQueue that the program has modified the position of |
`unspecified-bool-type`` contains(const T& t) const` |
Returns
whether the queue contains |
Concept Checking Class
boost/graph/buffer_concepts.hpp
template <class Q>
struct UpdatableQueueConcept
{
void constraints() {
BOOST_CONCEPT_ASSERT(( Buffer<Q> ));
q.update(g_ct);
}
void const_constraints(const Q& cq) {
if (cq.contains(g_ct));
}
static const typename Buffer<Q>::value_type g_ct;
Q q;
};UpdatablePriorityQueue
An UpdatablePriorityQueue is a slight refinement of
UpdatableQueue that imposes the
requirement that a program may not increase the position of a value that
is held in the queue. That is, if a value v had position n in the
ordering, a program may update the position of v only to 0, 1, …,
n - 1, or n, where 0 is the top of the queue.
The behavior when a program attempts to increase a value’s position in the ordering is undefined.