uk.ac.sheffield.vtts.model

Class Membership

java.lang.Object

uk.ac.sheffield.vtts.model.Element

uk.ac.sheffield.vtts.model.Named

uk.ac.sheffield.vtts.model.Expression

uk.ac.sheffield.vtts.model.Function

uk.ac.sheffield.vtts.model.Predicate

uk.ac.sheffield.vtts.model.Membership

public class Membership
extends Predicate

Membership represents a cardinality or membership predicate on a collection. There are six membership operators: isEmpty, notEmpty, includes, excludes, includesAll, excludesAll. The first operand is expected to be some kind of collection. The second operand is either absent (isEmpty, notEmpty), or an element (includes, excludes), or another collection (includesAll, excludesAll), or an arbitrary key (includesKey, excludesKey).

Version:

Broker@Cloud 1.0

Author:

Anthony J H Simons

Field Summary

Fields inherited from class uk.ac.sheffield.vtts.model.Function

expressions, maxOperands

Fields inherited from class uk.ac.sheffield.vtts.model.Expression

factory, type

Fields inherited from class uk.ac.sheffield.vtts.model.Named

name

Constructor Summary

Constructors

Constructor and Description
Membership() Creates a default Membership predicate.
Membership(java.lang.String name) Creates a named Membership predicate.

Method Summary

Methods

Modifier and Type	Method and Description
java.lang.Boolean	evaluate() Executes this Membership predicate on its operands.
protected java.lang.Boolean	excludes(java.lang.Object collection, java.lang.Object value) Reports whether the collection excludes the value from its elements.
protected java.lang.Boolean	excludesAll(java.lang.Object first, java.lang.Object second) Reports whether the first collection excludes all of the second one.
protected java.lang.Boolean	excludesKey(java.lang.Object collection, java.lang.Object key) Reports whether the map excludes the key from its search keys.
protected java.lang.Boolean	includes(java.lang.Object collection, java.lang.Object value) Reports whether the collection includes the value in its elements.
protected java.lang.Boolean	includesAll(java.lang.Object first, java.lang.Object second) Reports whether the first collection includes all of the second one.
protected java.lang.Boolean	includesKey(java.lang.Object collection, java.lang.Object key) Reports whether the collection includes the key in its search keys.
boolean	isConsistent() Reports whether this Membership predicate is consistent.
protected java.lang.Boolean	isEmpty(java.lang.Object collection) Reports whether the collection is empty.
protected void	nameCheck() Checks the name of this Membership predicate and sets the expected number of operands.
Predicate	negate() Returns the complement of this Membership predicate.
protected java.lang.Boolean	notEmpty(java.lang.Object collection) Reports whether the collection is not empty.
protected void	rebindFalse() Rebinds the unbound operands of this Membership predicate, so that it yields false.
protected void	rebindTrue() Rebinds the unbound operands of this Membership predicate, so that it yields true.
boolean	subsumes(Predicate other) Tests whether this Membership predicate subsumes the other Predicate.
protected boolean	subsumesMembership(Membership other) Reports whether this Membership predicate subsumes the other.
protected void	typeCheck() Checks that the operand types are consistent and that the result type is Boolean.

Methods inherited from class uk.ac.sheffield.vtts.model.Predicate

isFalseConstant, normalise, rebind, rebind, refine, setType, subsumesAllDisjunctsOf, subsumesOneConjunctOf, subsumesProposition

Methods inherited from class uk.ac.sheffield.vtts.model.Function

addExpression, assign, equals, getExpressions, getType, hashCode, isAssignable, isBound, operand, resolve, setName, toString, unbind

Methods inherited from class uk.ac.sheffield.vtts.model.Expression

getName, isBottom, isOrdered

Methods inherited from class uk.ac.sheffield.vtts.model.Named

setName

Methods inherited from class uk.ac.sheffield.vtts.model.Element

safeEquals, safeHashCode, semanticError

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

Membership

public Membership()

Creates a default Membership predicate.

Membership

public Membership(java.lang.String name)

Creates a named Membership predicate. Ensures that the name is one of the allowed membership operators.

Parameters:

name - the name of the membership predicate.

Method Detail

nameCheck

protected void nameCheck()

Checks the name of this Membership predicate and sets the expected number of operands. All Membership predicates expect two operands, apart from isEmpty and notEmpty, which expect one operand.

Specified by:

nameCheck in class Function

typeCheck

protected void typeCheck()

Checks that the operand types are consistent and that the result type is Boolean. The operand(0) type must be a collection. Depending on the operation, the operand(1) type must either be the same collection type; or the value-type, or the key-type of operand(0). Caches the value of paramType, valueType, keyType and pairType for use during binding and value synthesis. Caches the kind of collection, for dispatching during evaluation.

Specified by:

typeCheck in class Function

isConsistent

public boolean isConsistent()

Reports whether this Membership predicate is consistent. Returns false in the four cases: includes(bottom, x), includesAll(bottom, y), includesKey(bottom, z) and notEmpty(bottom), where bottom is the Constant representing an empty collection. Otherwise returns true.

Overrides:

isConsistent in class Predicate

Returns:

true if this Membership predicate is consistent.

subsumes

public boolean subsumes(Predicate other)

Tests whether this Membership predicate subsumes the other Predicate. If the other is also a Membership predicate, tests whether this subsumes the other. If the other is an AND-Proposition, tests whether this Membership predicate subsumes one of the other's conjuncts. Otherwise returns false.

Specified by:

subsumes in class Predicate

Parameters:

other - the other Predicate.

Returns:

true if this subsumes the other Predicate.

subsumesMembership

protected boolean subsumesMembership(Membership other)

Reports whether this Membership predicate subsumes the other. This is only true if the predicates are equal (we cannot currently reason about includesAll subsuming includes).

Parameters:

other - the other Membership predicate.

Returns:

true, if this Membership subsumes the other Membership.

negate

public Predicate negate()

Returns the complement of this Membership predicate. Converts pairwise between the predicates isEmpty/notEmpty, includes/excludes and includesKey/excludesKey. The two predicates includesAll and excludesAll cannot be so simply complemented, so are wrapped in a negated Proposition.

Overrides:

negate in class Predicate

Returns:

the logical complement of this Membership predicate.

evaluate

public java.lang.Boolean evaluate()

Executes this Membership predicate on its operands. Checks the consistency of the operand types and then branches according to the number of operands, and the name of this Membership predicate.

Specified by:

evaluate in class Predicate

Returns:

true, if the predicate holds between the operands.

isEmpty

protected java.lang.Boolean isEmpty(java.lang.Object collection)

Reports whether the collection is empty. Casts the argument to a Collection or a Map, and then calls Java's built-in method isEmpty().

Parameters:

collection - any kind of collection.

Returns:

true, if the collection is empty.

notEmpty

protected java.lang.Boolean notEmpty(java.lang.Object collection)

Reports whether the collection is not empty. Returns the logical negation of: isEmpty(collection).

Parameters:

collection - any kind of collection.

Returns:

true, if the collection is not empty.

includes

protected java.lang.Boolean includes(java.lang.Object collection,
                         java.lang.Object value)

Reports whether the collection includes the value in its elements. If the collection argument is a List or a Set, casts this to a Collection then calls Java's built-in method contains(); otherwise casts it to a Map, extracts the entrySet() and tests whether this contains() the supplied entry.

Parameters:

collection - any kind of collection.

value - any value of the collection's value-type.

Returns:

true, if the value is an element of the collection.

excludes

protected java.lang.Boolean excludes(java.lang.Object collection,
                         java.lang.Object value)

Reports whether the collection excludes the value from its elements. Returns the logical negation of: includes(collection, value).

Parameters:

collection - any kind of collection.

value - any value of the collection's value-type.

Returns:

true, if the value is not an element of the collection.

includesAll

protected java.lang.Boolean includesAll(java.lang.Object first,
                            java.lang.Object second)

Reports whether the first collection includes all of the second one. If the first and second arguments are Lists or Sets, casts these both to Collections, then calls Java's built-in method: containsAll(); otherwise casts both arguments to Maps, extracts the entrySet() from each and tests for inclusion using containsAll().

Parameters:

first - the first collection of any kind.

second - the second collection of the same kind.

Returns:

true, if all elements of the second are also in the first collection.

excludesAll

protected java.lang.Boolean excludesAll(java.lang.Object first,
                            java.lang.Object second)

Reports whether the first collection excludes all of the second one. If the first and second arguments are Lists or Sets, casts these both to Collections, then tests that no element from the second exists in the first, using Java's built-in method: contains(); otherwise, casts both arguments to Maps, extracts the entrySet() from each, and tests whether the first excludes every entry of the second.

Parameters:

first - the first collection of any kind.

second - the second collection of the same kind.

Returns:

true, if no elements of the second are also in the first collection.

includesKey

protected java.lang.Boolean includesKey(java.lang.Object collection,
                            java.lang.Object key)

Reports whether the collection includes the key in its search keys. For a Map, casts the collection to a Map, then calls Java's built-in method: containsKey(). For a list, casts the collection to a List and the key to an Integer, then checks if this index is in range.

Parameters:

collection - must be a Map or a List.

key - a key of the Map's key-type, or an Integer index.

Returns:

true, if the key is present in the collection's search keys.

excludesKey

protected java.lang.Boolean excludesKey(java.lang.Object collection,
                            java.lang.Object key)

Reports whether the map excludes the key from its search keys. Returns the logical negation of: includesKey(map, key).

Parameters:

collection - must be a Map or a List.

key - a key of the Map's key-type, or an Integer index.

Returns:

true, if the key is absent from the collection's search keys.

rebindTrue

protected void rebindTrue()

Rebinds the unbound operands of this Membership predicate, so that it yields true. If either operand is unbound, binds it to a value satisfying the constraint with respect to the other operand. If both are unbound, first binds the second operand to a default value.

Specified by:

rebindTrue in class Predicate

rebindFalse

protected void rebindFalse()

Rebinds the unbound operands of this Membership predicate, so that it yields false. If either operand is unbound, binds it to a value that violates the constraint with respect to the other operand. If both are unbound, first binds the second operand to a default value.

Specified by:

rebindFalse in class Predicate