ArcEager.java

package org.maltparser.parser.algorithm.nivre;

import java.util.Stack;
import org.maltparser.core.exception.MaltChainedException;
import org.maltparser.core.syntaxgraph.edge.Edge;
import org.maltparser.core.syntaxgraph.node.DependencyNode;
import org.maltparser.parser.ParserConfiguration;
import org.maltparser.parser.TransitionSystem;
import org.maltparser.parser.history.GuideUserHistory;
import org.maltparser.parser.history.History;
import org.maltparser.parser.history.action.ComplexDecisionAction;
import org.maltparser.parser.history.action.GuideUserAction;
import org.maltparser.parser.transition.TransitionTable;

/**
 * @author Johan Hall
 *
 */
public class ArcEager extends TransitionSystem {

    protected static final int SHIFT = 1;
    protected static final int REDUCE = 2;
    protected static final int RIGHTARC = 3;
    protected static final int LEFTARC = 4;

    public ArcEager() throws MaltChainedException {
        super();
    }

    public void apply(GuideUserAction currentAction, ParserConfiguration config) throws MaltChainedException {
        final NivreConfig nivreConfig = (NivreConfig) config;
        final Stack<DependencyNode> stack = nivreConfig.getStack();
        final Stack<DependencyNode> input = nivreConfig.getInput();
        currentAction.getAction(actionContainers);
        Edge e;
        switch (transActionContainer.getActionCode()) {
            case LEFTARC:
                e = nivreConfig.getDependencyStructure().addDependencyEdge(input.peek().getIndex(), stack.peek().getIndex());
                addEdgeLabels(e);
                stack.pop();
//			doPropagation(e);
                break;
            case RIGHTARC:
                e = nivreConfig.getDependencyStructure().addDependencyEdge(stack.peek().getIndex(), input.peek().getIndex());
                addEdgeLabels(e);
                stack.push(input.pop());
//			doPropagation(e);
                break;
            case REDUCE:
                stack.pop();
                break;
            default:
                stack.push(input.pop());
                break;
        }
    }

    public GuideUserAction getDeterministicAction(GuideUserHistory history, ParserConfiguration config) throws MaltChainedException {
        final NivreConfig nivreConfig = (NivreConfig) config;
        if (!nivreConfig.isAllowRoot() && nivreConfig.getStack().peek().isRoot()) {
            return updateActionContainers(history, ArcEager.SHIFT, null);
        }
        return null;
    }

    protected void addAvailableTransitionToTable(TransitionTable ttable) throws MaltChainedException {
        ttable.addTransition(SHIFT, "SH", false, null);
        ttable.addTransition(REDUCE, "RE", false, null);
        ttable.addTransition(RIGHTARC, "RA", true, null);
        ttable.addTransition(LEFTARC, "LA", true, null);
    }

    protected void initWithDefaultTransitions(GuideUserHistory history) throws MaltChainedException {
        GuideUserAction currentAction = new ComplexDecisionAction((History) history);

        transActionContainer.setAction(SHIFT);
        transActionContainer.setAction(REDUCE);
        for (int i = 0; i < arcLabelActionContainers.length; i++) {
            arcLabelActionContainers[i].setAction(-1);
        }
        currentAction.addAction(actionContainers);
    }

    public String getName() {
        return "nivreeager";
    }

    public boolean permissible(GuideUserAction currentAction, ParserConfiguration config) throws MaltChainedException {
        currentAction.getAction(actionContainers);
        final int trans = transActionContainer.getActionCode();
        final DependencyNode stackPeek = ((NivreConfig) config).getStack().peek();
        if ((trans == LEFTARC || trans == RIGHTARC) && !isActionContainersLabeled()) {
            return false;
        }
        if ((trans == LEFTARC || trans == REDUCE) && stackPeek.isRoot()) {
            return false;
        }
        if (trans == LEFTARC && stackPeek.hasHead()) {
            return false;
        }
        if (trans == REDUCE && !stackPeek.hasHead() && !((NivreConfig) config).isAllowReduce()) {
            return false;
        }
        return true;
    }

    public GuideUserAction defaultAction(GuideUserHistory history, ParserConfiguration configuration) throws MaltChainedException {
        return updateActionContainers(history, ArcEager.SHIFT, null);
    }
}