org.jacop.set.constraints

Class Lex

java.lang.Object

org.jacop.constraints.DecomposedConstraint

org.jacop.constraints.Constraint

org.jacop.set.constraints.Lex

public class Lex
extends Constraint

It creates a lex constraint on a list of set variables. Each consecutive pair of set variables is being constrained to be lexicographically ordered. For example, {}

Version:

4.2

Author:

Radoslaw Szymanek and Krzysztof Kuchcinski

Field Summary

Fields

Modifier and Type	Field and Description
SetVar	a It specifies a list on which element a lex relationship holds for every two consecutive variables.
SetVar	b It specifies a list on which element a lex relationship holds for every two consecutive variables.
protected int	inclusionLevel
protected TimeStamp<IntDomain>	inDifference
protected int	inSupport
protected TimeStamp<IntDomain>	smallerDifference
protected int	smallerElLevel
protected int	smallerElSupport
boolean	strict It specifies if the relation is strict or not.
static String[]	xmlAttributes It specifies the arguments required to be saved by an XML format as well as the constructor being called to recreate an object from an XML format.

Fields inherited from class org.jacop.constraints.Constraint

atomicExecution, consistencyPruningEvents, earlyTerminationOK, id, increaseWeight, numberArgs, numberId, trace

Fields inherited from class org.jacop.constraints.DecomposedConstraint

queueIndex

Constructor Summary

Constructors

Constructor and Description
Lex(SetVar a, SetVar b) It constructs an Lexical ordering constraint to restrict the domain of the variables a and b.
Lex(SetVar a, SetVar b, boolean strict) It constructs an Lexical ordering constraint to restrict the domain of the variables a and b.

Method Summary

Modifier and Type	Method and Description
ArrayList<Var>	arguments() It returns the variables in a scope of the constraint.
void	consistency(Store store) It is a (most probably incomplete) consistency function which removes the values from variables domains.
int	getConsistencyPruningEvent(Var var) It retrieves the pruning event which causes reevaluation of the constraint.
String	id() It gives the id string of a constraint.
void	impose(Store store) It imposes the constraint in a given store.
void	increaseWeight() It increases the weight of the variables in the constraint scope.
void	removeConstraint() It removes the constraint by removing this constraint from all variables.
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

cleanAfterFailure, decompose, getGuideConstraint, getGuideValue, getGuideVariable, impose, imposeDecomposition, numberArgs, queueVariable, removeLevelLate, requiresMonotonicity, setConsistencyPruningEvent, supplyGuideFeedback

Methods inherited from class org.jacop.constraints.DecomposedConstraint

auxiliaryVariables, derivative, imposeDecomposition

Methods inherited from class java.lang.Object

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

Field Detail

a

public SetVar a

It specifies a list on which element a lex relationship holds for every two consecutive variables.

b

public SetVar b

It specifies a list on which element a lex relationship holds for every two consecutive variables.

strict

public boolean strict

It specifies if the relation is strict or not.

xmlAttributes

public static String[] xmlAttributes

It specifies the arguments required to be saved by an XML format as well as the constructor being called to recreate an object from an XML format.

inSupport

protected int inSupport

inclusionLevel

protected int inclusionLevel

inDifference

protected TimeStamp<IntDomain> inDifference

smallerElSupport

protected int smallerElSupport

smallerElLevel

protected int smallerElLevel

smallerDifference

protected TimeStamp<IntDomain> smallerDifference

Constructor Detail

Lex

public Lex(SetVar a,
           SetVar b)

It constructs an Lexical ordering constraint to restrict the domain of the variables a and b. It is strict by default.

Parameters:

a - variable that is restricted to be less than b with lexical order.

b - variable that is restricted to be greater than a with lexical order.

Lex

public Lex(SetVar a,
           SetVar b,
           boolean strict)

It constructs an Lexical ordering constraint to restrict the domain of the variables a and b.

Parameters:

a - variable that is restricted to be less than b with lexical order.

b - variable that is restricted to be greater than a with lexical order.

strict - specifies if the lex relation is strict.

Method Detail

arguments

public ArrayList<Var> arguments()

Description copied from class: Constraint

It returns the variables in a scope of the constraint.

Specified by:

arguments in class Constraint

Returns:

variables in a scope of the constraint.

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.

getConsistencyPruningEvent

public int getConsistencyPruningEvent(Var var)

Description copied from class: Constraint

It retrieves the pruning event which causes reevaluation of the constraint.

Specified by:

getConsistencyPruningEvent in class Constraint

Parameters:

var - variable for which pruning event is retrieved

Returns:

it returns the int code of the pruning event (GROUND, BOUND, ANY, NONE)

id

public String id()

Description copied from class: Constraint

It gives the id string of a constraint.

Overrides:

id in class Constraint

Returns:

string id of the constraint.

impose

public void impose(Store store)

Description copied from class: Constraint

It imposes the constraint in a given store.

Specified by:

impose in class Constraint

Parameters:

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

removeLevel

public void removeLevel(int level)

Description copied from class: Constraint

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.

Overrides:

removeLevel in class Constraint

Parameters:

level - the level which is being removed.

removeConstraint

public void removeConstraint()

Description copied from class: Constraint

It removes the constraint by removing this constraint from all variables.

Specified by:

removeConstraint in class Constraint

satisfied

public boolean satisfied()

Description copied from class: Constraint

It checks if the constraint is satisfied. If this function is incorrectly implemented a constraint may not be satisfied in a solution.

Specified by:

satisfied in class Constraint

Returns:

true if the constraint is for certain satisfied, false otherwise.

toString

public String toString()

Description copied from class: Constraint

It produces a string representation of a constraint state.

Specified by:

toString in class Constraint

increaseWeight

public void increaseWeight()

Description copied from class: Constraint

It increases the weight of the variables in the constraint scope.

Specified by:

increaseWeight in class Constraint