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Interface ObjectSet

All Superinterfaces:

java.util.Collection, java.lang.Iterable, java.util.Set

All Known Implementing Classes:

AbstractObjectSet, DefaultObjectSet, POPAppBasedSet

public interface ObjectSet
extends java.util.Set

Interface for sets of objects in a partial world. Each ObjectSet is backed by a particular partial world. It extends the Java Set interface in several ways:

• Sampling: An ObjectSet has a sample method that returns an element sampled uniformly at random. This may be faster than iterating over the set until the Nth element is reached (for a random N).
• Indistinguishable objects: The iterator method on an ObjectSet returns an ObjectIterator, which has a special method for skipping objects that are indistinguishable (in the underlying partial world) from the last object returned. There is also an iterator method that takes a set of externally distinguished objects (typically the values of logical variables in the current scope), which are treated as distinguishable from all other objects.
• Partially defined sets: If a set is defined intensively (e.g., as the set of objects satisfying a particular formula), then a partial world may be complete enough to define the return values for certain methods on the set (such as isEmpty) but not complete enough to define the set fully. Thus, the ObjectSet interface includes methods canDetermineIsEmpty, canDetermineSize, canDetermineContains and canDetermineElements. If one of these methods returns false, then the behavior of the corresponding Set interface method(s) is undefined.

Field Summary

static ObjectSet	EMPTY_OBJECT_SET
static ObjectSet	UNDETERMINED_SET

Method Summary

boolean	canDetermineContains(java.lang.Object obj) Returns true if the underlying partial world is complete enough to determine whether the given object is in this set.
boolean	canDetermineElements() Returns true if the underlying partial world is complete enough to determine all the elements of this set.
boolean	canDetermineIsEmpty() Returns true if the underlying partial world is complete enough to determine whether this set is empty.
boolean	canDetermineSize() Returns true if the underlying partial world is complete enough to determine the size of this set.
ObjectSet	getExplicitVersion() Returns a version of this set that no longer reflects changes to the partial world or evaluation context.
int	indexOf(java.lang.Object o) Returns the number which, when passed to sample, will yield the given element of this set.
ObjectIterator	iterator(java.util.Set externallyDistinguished) Returns an ObjectIterator whose skipIndistinguishable method treats all of the given objects as distinguishable from all other objects, even if they are indistinguishable in the underlying partial world.
java.lang.Object	sample(int n) Returns an object sampled uniformly at random from this set, assuming that the given number n is sampled uniformly from the numbers 0, ..., size - 1 (where size is the size of this set).

Methods inherited from interface java.util.Set

add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray

Field Detail

EMPTY_OBJECT_SET

static final ObjectSet EMPTY_OBJECT_SET

UNDETERMINED_SET

static final ObjectSet UNDETERMINED_SET

Method Detail

sample

java.lang.Object sample(int n)

Returns an object sampled uniformly at random from this set, assuming that the given number n is sampled uniformly from the numbers 0, ..., size - 1 (where size is the size of this set).

If the underlying partial world is not complete enough to fully define this set, this method returns null.

Throws:

java.lang.IllegalArgumentException - if n is less than 0 or greater than or equal to the size of this set

indexOf

int indexOf(java.lang.Object o)

Returns the number which, when passed to sample, will yield the given element of this set. If the given object is not in this set, returns -1.

If the underlying partial world is not complete enough to fully define this set, this method returns -1.

iterator

ObjectIterator iterator(java.util.Set externallyDistinguished)

Returns an ObjectIterator whose skipIndistinguishable method treats all of the given objects as distinguishable from all other objects, even if they are indistinguishable in the underlying partial world. These externally distinguishable objects are typically the values of logical variables in the current scope -- the point is that even if the partial world makes the same assertions about two objects, these objects may satisfy different formulas if one is the value of a currently bound variable and one is not.

canDetermineIsEmpty

boolean canDetermineIsEmpty()

Returns true if the underlying partial world is complete enough to determine whether this set is empty.

canDetermineSize

boolean canDetermineSize()

Returns true if the underlying partial world is complete enough to determine the size of this set.

canDetermineContains

boolean canDetermineContains(java.lang.Object obj)

Returns true if the underlying partial world is complete enough to determine whether the given object is in this set.

canDetermineElements

boolean canDetermineElements()

Returns true if the underlying partial world is complete enough to determine all the elements of this set.

getExplicitVersion

ObjectSet getExplicitVersion()

Returns a version of this set that no longer reflects changes to the partial world or evaluation context. It may still be backed by a world's POP application satisfier sets (so that new identifiers are added properly), but other than that, its methods will not call any methods on the underlying partial world.

This method returns null if the underlying partial world is not complete enough to construct an explicit version of this set.