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Open-source constraint solver.
/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2023, IMT Atlantique. All rights reserved.
*
* Licensed under the BSD 4-clause license.
*
* See LICENSE file in the project root for full license information.
*/
package org.chocosolver.solver.variables;
import org.chocosolver.memory.IEnvironment;
import org.chocosolver.solver.ICause;
import org.chocosolver.solver.Identity;
import org.chocosolver.solver.Model;
import org.chocosolver.solver.constraints.Propagator;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.propagation.PropagationEngine;
import org.chocosolver.solver.variables.delta.IDelta;
import org.chocosolver.solver.variables.events.IEventType;
import org.chocosolver.solver.variables.view.IView;
import org.chocosolver.util.iterators.EvtScheduler;
import java.util.function.BiConsumer;
import java.util.stream.Stream;
/**
* To developers: any constructor of variable must pass in parameter
* the back-end ISolver, that is, in decreasing order:
* - the model portfolio,
* - the model (or portfolio workers but fes).
* Created by IntelliJ IDEA.
* User: xlorca, Charles Prud'homme
*/
public interface Variable extends Identity, Comparable {
/**
* Type of variable: variable (unique).
*/
int VAR = 1;
/**
* Type of variable: fixed (unique).
*/
int CSTE = 1 << 1;
/**
* Type of variable: view (unique).
*/
int VIEW = 1 << 2;
/**
* Mask to get the type of a variable.
*/
int TYPE = (1 << 3) - 1;
/**
* Kind of variable: integer (unique).
*/
int INT = 1 << 3;
/**
* Kind of variable: boolean and integer too (unique).
*/
int BOOL = INT | (1 << 4);
/**
* Kind of variable: set.
*/
int SET = 1 << 5;
/**
* Kind of variable: real.
*/
int REAL = 1 << 6;
/**
* Kind of variable: graph.
*/
int GRAPH = 1 << 7;
/**
* Mask to get the kind of a variable.
*/
int KIND = (1 << 10) - 1 - TYPE;
/**
* Indicates whether this is instantiated (see implementations to know what instantiation means).
*
* @return true if this is instantiated
*/
boolean isInstantiated();
/**
* Returns the size of this domain, that is the number of elements in this domain.
*
* @return size of the domain
*/
int getDomainSize();
/**
* Return the world index at which this variable has been instantiated is returned.
* If the variable is not instantiated, then it returns {@link Integer#MAX_VALUE}, that
* is a value greater than the current world index.
*
* @return the world index at which this variable has been instantiated is returned or
* {@link Integer#MAX_VALUE}.
* @implNote
* Indeed, a call to {@link #recordWorldIndex()}
* is only when the variable becomes fixed (ie, instantiated),
* but nothing is (un)done upon backtrack, when the variable becomes free again.
*
* For constant, a call to this method returns 0.
* @see #recordWorldIndex()
* @see Model#getEnvironment()
* @see IEnvironment#getWorldIndex()
*/
int instantiationWorldIndex();
/**
* Record the world index at which this variable has been instantiated.
*
* @see #instantiationWorldIndex()
* @see Model#getEnvironment()
* @see IEnvironment#getWorldIndex()
*/
void recordWorldIndex();
/**
* Returns the name of this
*
* @return a String representing the name of this
*/
String getName();
/**
* @return a stream of the propagators of this variable
*/
Stream> streamPropagators();
/**
* Performs an action for each propagator of this variable.
*
* @param action action to perform on the elements
*/
void forEachPropagator(BiConsumer> action);
/**
* Return the number of propagators
*
* @return number of propagators of this
*/
int getNbProps();
/**
* Build and add a monitor to the monitor list of this.
* The monitor is inactive at the creation and must be activated (by the engine propagation).
*
* @param monitor a variable monitor
*/
void addMonitor(IVariableMonitor monitor);
/**
* Removes monitor form the list of this variable's monitors.
*
* @param monitor the monitor to remove.
*/
@SuppressWarnings("unused")
void removeMonitor(IVariableMonitor monitor);
/**
* Attaches a view to this variable.
*
* @param view a view to add to this variable.
* @param idx the index of this variable in the view's array of observed variables
*/
void subscribeView(IView view, int idx);
/**
* Return the delta domain of this
*
* @return the delta domain of the variable
*/
IDelta getDelta();
/**
* Create a delta, if necessary, in order to observe removed values of a this.
* If the delta already exists, has no effect.
*/
void createDelta();
/**
* Link the propagator to this
*
* @param propagator a newly added propagator
* @param idxInProp index of the variable in the propagator
*/
void link(Propagator propagator, int idxInProp);
/**
* The propagator will not be informed of any modification of this anymore.
*
* @param propagator the propagator to swap
* @param idxInProp index of the variable in the propagator
*/
void swapOnPassivate(Propagator propagator, int idxInProp);
/**
* Remove a propagator from the list of propagator of this.
* SHOULD BE CONTAINED IN THIS.
*
* @param propagator the propagator to remove
* @param idxInProp index of the variable in the propagator
*/
void unlink(Propagator propagator, int idxInProp);
/**
* If this has changed, then notify all of its observers.
* Each observer has its update method.
*
* @param event event on this object
* @param cause object which leads to the modification of this object
* @throws ContradictionException if a contradiction occurs during notification
*/
void notifyPropagators(IEventType event, ICause cause) throws ContradictionException;
/**
* Notify views of observed variable modifications
*
* @param event the event which occurred on the variable
* @param cause the cause of the notification
* @throws ContradictionException if the notification detects contradiction.
*/
void notifyViews(IEventType event, ICause cause) throws ContradictionException;
/**
* @return the number of views attached to the variable
*/
int getNbViews();
/**
* Get the view at position p in this variable views.
* The array is filled from position 0 to position {@link #getNbViews()} excluded.
*
* @param p position of the view to return
* @return view observing this variable, at position p
*/
IView getView(int p);
/**
* Notify monitors of observed variable modifications
*
* @param event the event which occurred on the variable
* @throws ContradictionException if the monitor detects contradiction.
*/
void notifyMonitors(IEventType event) throws ContradictionException;
/**
* Throws a contradiction exception based on
*
* @param cause ICause causing the exception
* @param message the detailed message @throws ContradictionException expected behavior
* @throws ContradictionException the build contradiction.
*/
void contradiction(ICause cause, String message) throws ContradictionException;
/**
* Return the associated model
*
* @return a Model object
*/
Model getModel();
/**
* @return the backtracking environment used for this variable
*/
default IEnvironment getEnvironment() {
return getModel().getEnvironment();
}
/**
* Return a MASK composed of 2 main information: TYPE and KIND.
*
TYPE is defined in the 3 first bits : VAR ( 1 << 0), CSTE (1 << 1) or VIEW (1 << 2)
*
KIND is defined on the other bits : INT (1 << 3), BOOL (INT + 1 << 4), GRAPH (1 << 5) or META (1 << 6)
*
*
* To get the TYPE of a variable:
*
* int type = var.getTypeAndKind() & Variable.TYPE;
*
*
* To get the KIND of a variable:
*
* int kind = var.getTypeAndKind() & Variable.KIND;
*
*
* To check a specific type or kind of a variable:
*
* boolean isVar = (var.getTypeAndKind() & Variable.VAR) !=0;
* boolean isInt = (var.getTypeAndKind() & Variable.INT) !=0;
*
*
* @return an int representing the type and kind of the variable
*/
int getTypeAndKind();
/**
* @return true iff the variable is a constant (created with a singleton domain)
*/
boolean isAConstant();
/**
* For scheduling purpose only
*
* @return the scheduler
*/
EvtScheduler getEvtScheduler();
/**
* @return true if related propagators are scheduled for propagation
*/
boolean isScheduled();
/**
* Set this as scheduled
*/
void schedule();
/**
* Set this as unscheduled
*/
void unschedule();
/**
* Schedule active propagators in the engine
*/
void schedulePropagators(PropagationEngine engine);
/**
* @return this cast into an IntVar.
* @throws ClassCastException if type is not compatible
*/
IntVar asIntVar();
/**
* @return this cast into an BoolVar.
* @throws ClassCastException if type is not compatible
*/
BoolVar asBoolVar();
/**
* @return this cast into an RealVar.
* @throws ClassCastException if type is not compatible
*/
RealVar asRealVar();
/**
* @return this cast into an SetVar.
* @throws ClassCastException if type is not compatible
*/
SetVar asSetVar();
/**
* Temporarily store modification events made on this.
* This is required by the propagation engine.
*
* @param mask event's mask
* @param cause what causes the modification (cannot be null)
*/
void storeEvents(int mask, ICause cause);
/**
* Clear events stored temporarily by {@link #storeEvents(int, ICause)}
*/
void clearEvents();
/**
* @return possibly aggregated mask stored through by {@link #storeEvents(int, ICause)}
*/
int getMask();
/**
* @return cause stored through by {@link #storeEvents(int, ICause)} or {@link org.chocosolver.solver.Cause#Null}
* if different causes modified this variable (this may happen when a view refers to this).
*/
ICause getCause();
}