com.thesett.aima.logic.fol.wam.compiler.WAMCompiledClause Maven / Gradle / Ivy

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/*
 * Copyright The Sett Ltd, 2005 to 2014.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.thesett.aima.logic.fol.wam.compiler;

import java.util.Arrays;

import com.thesett.aima.logic.fol.Clause;
import com.thesett.aima.logic.fol.Functor;
import com.thesett.common.util.SizeableList;

/**
 * WAMCompiledClause is a clause, that belongs to an {@link WAMCompiledPredicate}. Compiled instructions added to the
 * clause fall through onto the parent predicate, and are not held on the compiled clause itself. The compiled clause
 * has a label, which identifies its position within the parent predicate.
 *
 * 
 * CRC Card Responsibilities  Collaborations
 * 
 Forward added instructions onto the parent predicate.
 * 
 Hold a label as a position marker for the clause within its containing predicate.
 * 
 *
 * @author Rupert Smith
 */
public class WAMCompiledClause extends Clause
{
    /** The parent predicate to which this compiled clause belongs. */
    private final WAMCompiledPredicate parent;

    /** The interned name of this clauses label. */
    int label;

    /** Indicates that this has been added to a parent predicate already. */
    private boolean addedToParent = false;

    /**
     * Creates a clause within a parent predicate.
     *
     * @param parent The parent predicate.
     */
    public WAMCompiledClause(WAMCompiledPredicate parent)
    {
        super(null, null);
        this.parent = parent;
    }

    /**
     * Adds a conjunctive body functor, or head functor, to this clause, along with the instructions that implement it.
     *
     * @param body         A conjunctive body functor to add to this clause.
     * @param instructions A list of instructions to add to the body.
     */
    public void addInstructions(Functor body, SizeableList instructions)
    {
        int oldLength;

        if (this.body == null)
        {
            oldLength = 0;
            this.body = new Functor[1];
        }
        else
        {
            oldLength = this.body.length;
            this.body = Arrays.copyOf(this.body, oldLength + 1);
        }

        this.body[oldLength] = body;

        addInstructionsAndThisToParent(instructions);
    }

    /**
     * Adds some instructions sequentially, after any existing instructions, to the clause.
     *
     * @param instructions The instructions to add to the clause.
     */
    public void addInstructions(SizeableList instructions)
    {
        addInstructionsAndThisToParent(instructions);
    }

    /**
     * Adds some instructions to the parent predicate, and also adds this as a clause on the parent, if it has not
     * already been added.
     *
     * @param instructions The instructions to add.
     */
    private void addInstructionsAndThisToParent(SizeableList instructions)
    {
        if (!addedToParent)
        {
            parent.addInstructions(this, instructions);
            addedToParent = true;
        }
        else
        {
            parent.addInstructions(instructions);
        }
    }
}
Responsibilities	Collaborations *
Forward added instructions onto the parent predicate. *
Hold a label as a position marker for the clause within its containing predicate. *