Constraint.java

  1. /* Copyright 2015 Laurent COCAULT
  2.  * Licensed to Laurent COCAULT under one or more contributor license agreements.
  3.  * See the NOTICE file distributed with this work for additional information
  4.  * regarding copyright ownership. Laurent COCAULT licenses this file to You
  5.  * under the Apache License, Version 2.0 (the "License"); you may not use this
  6.  * file except in compliance with the License.  You may obtain a copy of the
  7.  * License at
  8.  *
  9.  *   http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  17. package org.csp.constraint.model;

  19. /**
  20.  * Represents a constraint of a constraint solving problem.
  21.  */
  22. public abstract class Constraint<T> {

  24.     /** Name of the constraint. */
  25.     private String name_;

  27.     /** Enable the constraint to propagate. */
  28.     private boolean enablePropagate_;

  30.     /**
  31.      * Constructor.
  32.      * @param name
  33.      *            Name of the constraint
  34.      */
  35.     public Constraint(final String name) {
  36.         name_ = name;
  37.     }

  39.     /**
  40.      * Enable or disable the constraint propagation.
  41.      * @param enable
  42.      *            True if the constraint propagation is enabled, false otherwise
  43.      */
  44.     public void enablePropagate(final boolean enable) {
  45.         enablePropagate_ = enable;
  46.     }

  48.     /**
  49.      * Get the name of the constraint.
  50.      * @return The name of the constraint
  51.      */
  52.     public String getName() {
  53.         return name_;
  54.     }

  56.     /**
  57.      * Tests if the constraint is binary.
  58.      * @return True if the constraint is a binary constraint
  59.      */
  60.     public abstract boolean isBinary();

  62.     /**
  63.      * Tell if the propagation of the constraint is enabled.
  64.      * @return True if the constraint propagation is enabled
  65.      */
  66.     public boolean isPropagationEnabled() {
  67.         return enablePropagate_;
  68.     }

  70.     /**
  71.      * Tests if the constraint is ternary.
  72.      * @return True if the constraint is a ternary constraint
  73.      */
  74.     public abstract boolean isTernary();

  76.     /**
  77.      * Tests if the constraint is unary.
  78.      * @return True if the constraint is an unary constraint
  79.      */
  80.     public abstract boolean isUnary();

  82.     /**
  83.      * Tests if the constraint is unsized.
  84.      * @return True if the constraint is an unsized N-ary constraint
  85.      */
  86.     public abstract boolean isUnsized();

  88.     /**
  89.      * Indicates if the given variable is referenced by the constraint, ie if
  90.      * the constraint may reduce it.
  91.      * @param variable
  92.      *            Variable whose reference is checked
  93.      * @return True if the variable is referenced by the constraint
  94.      */
  95.     abstract boolean isVariableReferenced(Variable<T> variable);

  97.     /**
  98.      * Propagate the constraint (reduce the domain of each variable associated
  99.      * with the constraint).
  100.      */
  101.     public abstract void propagate();

  103.     /**
  104.      * Revise the constraint consistency.
  105.      * @return True if the constraint is consistent (the domain of each variable
  106.      *         associated with the constraint is not empty)
  107.      */
  108.     public abstract boolean revise();

  110.     /**
  111.      * {@inheritDoc}
  112.      */
  113.     @Override
  114.     public String toString() {
  115.         return name_;
  116.     }

  118. };
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