org.jacop.constraints

Class ElementVariable

java.lang.Object

org.jacop.constraints.DecomposedConstraint<Constraint>

org.jacop.constraints.Constraint

org.jacop.constraints.ElementVariable

All Implemented Interfaces:

SatisfiedPresent, Stateful, UsesQueueVariable

public class ElementVariable
extends Constraint
implements UsesQueueVariable, Stateful, SatisfiedPresent

ElementVariable constraint defines a relation list[index - indexOffset] = value.

The first element of the list corresponds to index - indexOffset = 1. By default indexOffset is equal 0 so first value within a list corresponds to index equal 1.

If index has a domain from 0 to list.length-1 then indexOffset has to be equal -1 to make addressing of list array starting from 1.

Version:

4.9

Author:

Krzysztof Kuchcinski and Radoslaw Szymanek

Field Summary

Fields

Modifier and Type	Field and Description
IntVar	index It specifies variable index within an element constraint list[index - indexOffset] = value.
int	indexOffset It specifies indexOffset within an element constraint list[index - indexOffset] = value.
IntVar[]	list It specifies list of variables within an element constraint list[index - indexOffset] = value.
IntVar	value It specifies variable value within an element constraint list[index - indexOffset] = value.

Fields inherited from class org.jacop.constraints.Constraint

atomicExecution, consistencyPruningEvents, constraintScope, earlyTerminationOK, increaseWeight, numberId, scope, trace

Fields inherited from class org.jacop.constraints.DecomposedConstraint

queueIndex

Constructor Summary

Constructors

Constructor and Description
ElementVariable(IntVar index, IntVar[] list, IntVar value) It constructs an element constraint.
ElementVariable(IntVar index, IntVar[] list, IntVar value, int indexOffset) It constructs an element constraint.
ElementVariable(IntVar index, List<? extends IntVar> list, IntVar value) It constructs an element constraint.
ElementVariable(IntVar index, List<? extends IntVar> list, IntVar value, int indexOffset) It constructs an element constraint.

Method Summary

Modifier and Type	Method and Description
void	consistency(Store store) It is a (most probably incomplete) consistency function which removes the values from variables domains.
int	getDefaultConsistencyPruningEvent()
void	impose(Store store) It imposes the constraint in a given store.
void	queueVariable(int level, Var var) This is a function called to indicate which variable in a scope of constraint has changed.
void	removeLevel(int level) This function is called in case of the backtrack, so a constraint can clear the queue of changed variables which is no longer valid.
boolean	satisfied() It checks if the constraint is satisfied.
String	toString() It produces a string representation of a constraint state.

Methods inherited from class org.jacop.constraints.Constraint

afc, arguments, cleanAfterFailure, decompose, getConsistencyPruningEvent, getGuideConstraint, getGuideValue, getGuideVariable, grounded, grounded, id, impose, imposeDecomposition, increaseWeight, intArrayToString, long2int, numberArgs, removeConstraint, requiresMonotonicity, setConsistencyPruningEvent, setConstraintScope, setScope, setScope, setScope, setScope, setScope, setWatchedVariableGrounded, supplyGuideFeedback, updateAFC, watchedVariableGrounded

Methods inherited from class org.jacop.constraints.DecomposedConstraint

auxiliaryVariables, checkInput, checkInput, checkInputForDuplication, checkInputForDuplicationSkipSingletons, checkInputForNullness, checkInputForNullness, checkInputForNullness, derivative, getDubletonsSkipSingletons, imposeDecomposition

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.jacop.api.Stateful

isStateful

Field Detail

index

public IntVar index

It specifies variable index within an element constraint list[index - indexOffset] = value.

value

public IntVar value

It specifies variable value within an element constraint list[index - indexOffset] = value.

indexOffset

public final int indexOffset

It specifies indexOffset within an element constraint list[index - indexOffset] = value.

list

public IntVar[] list

It specifies list of variables within an element constraint list[index - indexOffset] = value. The list is addressed by positive integers (>=1) if indexOffset is equal to 0.

Constructor Detail

ElementVariable

public ElementVariable(IntVar index,
                       IntVar[] list,
                       IntVar value,
                       int indexOffset)

It constructs an element constraint.

Parameters:

index - variable index

list - list of variables from which an index-th element is taken

value - a value of the index-th element from list

indexOffset - shift applied to index variable.

ElementVariable

public ElementVariable(IntVar index,
                       List<? extends IntVar> list,
                       IntVar value)

It constructs an element constraint.

Parameters:

index - variable index

list - list of variables from which an index-th element is taken

value - a value of the index-th element from list

ElementVariable

public ElementVariable(IntVar index,
                       List<? extends IntVar> list,
                       IntVar value,
                       int indexOffset)

It constructs an element constraint.

Parameters:

index - variable index

list - list of variables from which an index-th element is taken

value - a value of the index-th element from list

indexOffset - shift applied to index variable.

ElementVariable

public ElementVariable(IntVar index,
                       IntVar[] list,
                       IntVar value)

It constructs an element constraint.

Parameters:

index - variable index

list - list of variables from which an index-th element is taken

value - a value of the index-th element from list

Method Detail

removeLevel

public void removeLevel(int level)

Description copied from interface: Stateful

This function is called in case of the backtrack, so a constraint can clear the queue of changed variables which is no longer valid. This function is called *before* all timestamps, variables, mutablevariables have reverted to their previous value.

Specified by:

removeLevel in interface Stateful

Parameters:

level - the level which is being removed.

consistency

public void consistency(Store store)

Description copied from class: Constraint

It is a (most probably incomplete) consistency function which removes the values from variables domains. Only values which do not have any support in a solution space are removed.

Specified by:

consistency in class Constraint

Parameters:

store - constraint store within which the constraint consistency is being checked.

getDefaultConsistencyPruningEvent

public int getDefaultConsistencyPruningEvent()

Specified by:

getDefaultConsistencyPruningEvent in class Constraint

impose

public void impose(Store store)

Description copied from class: Constraint

It imposes the constraint in a given store.

Overrides:

impose in class Constraint

Parameters:

store - the constraint store to which the constraint is imposed to.

queueVariable

public void queueVariable(int level,
                          Var var)

Description copied from class: Constraint

This is a function called to indicate which variable in a scope of constraint has changed. It also indicates a store level at which the change has occurred.

Overrides:

queueVariable in class Constraint

Parameters:

level - the level of the store at which the change has occurred.

var - variable which has changed.

satisfied

public boolean satisfied()

Description copied from interface: SatisfiedPresent

It checks if the constraint is satisfied. It can return false even if constraint is satisfied but not all variables in its scope are grounded. It needs to return true if all variables in its scope are grounded and constraint is satisfied.

Implementations of this interface for constraints that are not PrimitiveConstraint may require constraint imposition and consistency check as a requirement to work correctly.

Specified by:

satisfied in interface SatisfiedPresent

Returns:

true if constraint is possible to verify that it is satisfied.

toString

public String toString()

Description copied from class: Constraint

It produces a string representation of a constraint state.

Overrides:

toString in class Constraint