    001    package org.maltparser.parser.algorithm.nivre;
    002
    003    import org.maltparser.core.exception.MaltChainedException;
    004    import org.maltparser.core.syntaxgraph.DependencyStructure;
    005    import org.maltparser.core.syntaxgraph.node.DependencyNode;
    006    import org.maltparser.parser.DependencyParserConfig;
    007    import org.maltparser.parser.Oracle;
    008    import org.maltparser.parser.ParserConfiguration;
    009    import org.maltparser.parser.history.GuideUserHistory;
    010    import org.maltparser.parser.history.action.GuideUserAction;
    011    /**
    012     * @author Johan Hall
    013     *
    014     */
    015    public class ArcEagerOracle extends Oracle {
    016
    017            public ArcEagerOracle(DependencyParserConfig manager, GuideUserHistory history) throws MaltChainedException {
    018                    super(manager, history);
    019                    setGuideName("ArcEager");
    020            }
    021
    022            public GuideUserAction predict(DependencyStructure gold, ParserConfiguration config) throws MaltChainedException {
    023                    final NivreConfig nivreConfig = (NivreConfig)config;
    024                    final DependencyNode stackPeek = nivreConfig.getStack().peek();
    025                    final int stackPeekIndex = stackPeek.getIndex();
    026                    final int inputPeekIndex = nivreConfig.getInput().peek().getIndex();
    027
    028                    if (!stackPeek.isRoot() && gold.getTokenNode(stackPeekIndex).getHead().getIndex() == inputPeekIndex) {
    029                            return updateActionContainers(ArcEager.LEFTARC, gold.getTokenNode(stackPeekIndex).getHeadEdge().getLabelSet());
    030                    } else if (gold.getTokenNode(inputPeekIndex).getHead().getIndex() == stackPeekIndex) {
    031                            return updateActionContainers(ArcEager.RIGHTARC, gold.getTokenNode(inputPeekIndex).getHeadEdge().getLabelSet());
    032                    } else if (nivreConfig.getRootHandling() == NivreConfig.STRICT && !stackPeek.hasHead()) {
    033                            return updateActionContainers(ArcEager.SHIFT, null);
    034                    } else if (gold.getTokenNode(inputPeekIndex).hasLeftDependent() &&
    035                                    gold.getTokenNode(inputPeekIndex).getLeftmostDependent().getIndex() < stackPeekIndex) {
    036                            return updateActionContainers(ArcEager.REDUCE, null);
    037                    } else if (gold.getTokenNode(inputPeekIndex).getHead().getIndex() < stackPeekIndex &&
    038                                    (!gold.getTokenNode(inputPeekIndex).getHead().isRoot() || nivreConfig.getRootHandling() == NivreConfig.NORMAL)) {
    039                            return updateActionContainers(ArcEager.REDUCE, null);
    040                    } else {
    041                            return updateActionContainers(ArcEager.SHIFT, null);
    042                    }
    043            }
    044
    045            public void finalizeSentence(DependencyStructure dependencyGraph) throws MaltChainedException {}
    046
    047            public void terminate() throws MaltChainedException {}
    048    }