com.thesett.aima.logic.fol.wam.machine.WAMEngine 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.machine;

import com.thesett.aima.logic.fol.Clause;
import com.thesett.aima.logic.fol.LogicCompiler;
import com.thesett.aima.logic.fol.Parser;
import com.thesett.aima.logic.fol.Resolver;
import com.thesett.aima.logic.fol.Sentence;
import com.thesett.aima.logic.fol.VariableAndFunctorInterner;
import com.thesett.aima.logic.fol.interpreter.ResolutionEngine;
import com.thesett.aima.logic.fol.isoprologparser.SentenceParser;
import com.thesett.aima.logic.fol.isoprologparser.Token;
import com.thesett.aima.logic.fol.isoprologparser.TokenSource;
import com.thesett.aima.logic.fol.wam.compiler.WAMCompiledPredicate;
import com.thesett.aima.logic.fol.wam.compiler.WAMCompiledQuery;
import com.thesett.common.parsing.SourceCodeException;
import com.thesett.common.util.Source;

/**
 * WAMEngine implements a {@link ResolutionEngine} for an WAM-based Prolog with built-ins. This engine loads its
 * standard library of built-ins from a resource on the classpath.
 *
 * 
 * CRC Card Responsibilities  Collaborations
 * 
 Load the Prolog built-in library from a resource on the classpath when the engine is reset.
 * 
 *
 * @author Rupert Smith
 */
public class WAMEngine extends ResolutionEngine
{
    /** Holds the name of the resource on the classpath that contains the built-in library. */
    private static final String BUILT_IN_LIB = "wam_builtins.pl";

    /**
     * Builds an logical resolution engine from a parser, interner, compiler and resolver.
     *
     * @param parser   The parser.
     * @param interner The interner.
     * @param compiler The compiler.
     * @param resolver The resolver.
     */
    public WAMEngine(Parser parser, VariableAndFunctorInterner interner,
        LogicCompiler compiler,
        Resolver resolver)
    {
        super(parser, interner, compiler, resolver);
    }

    /**
     * {@inheritDoc}
     *
     * Loads the built-in library resource specified by {@link #BUILT_IN_LIB}.
     */
    public void reset()
    {
        // Reset the resolver to completely clear out its domain.
        resolver.reset();

        // Create a token source to load the model rules from.
        Source tokenSource =
            TokenSource.getTokenSourceForInputStream(WAMEngine.class.getClassLoader().getResourceAsStream(
                    BUILT_IN_LIB));

        // Set up a parser on the token source.
        Parser libParser = new SentenceParser(interner);
        libParser.setTokenSource(tokenSource);

        // Load the built-ins into the domain.
        try
        {
            while (true)
            {
                Sentence sentence = libParser.parse();

                if (sentence == null)
                {
                    break;
                }

                compiler.compile(sentence);
            }

            compiler.endScope();
        }
        catch (SourceCodeException e)
        {
            // There should not be any errors in the built in library, if there are then the prolog engine just
            // isn't going to work, so report this as a bug.
            throw new RuntimeException("Got an exception whilst loading the built-in library.", e);
        }
    }
}