001    package org.maltparser.parser.algorithm.nivre;
002    
003    import java.util.Stack;
004    
005    import org.maltparser.core.exception.MaltChainedException;
006    import org.maltparser.core.syntaxgraph.edge.Edge;
007    import org.maltparser.core.syntaxgraph.node.DependencyNode;
008    import org.maltparser.parser.ParserConfiguration;
009    import org.maltparser.parser.TransitionSystem;
010    import org.maltparser.parser.history.GuideUserHistory;
011    import org.maltparser.parser.history.History;
012    import org.maltparser.parser.history.action.ComplexDecisionAction;
013    import org.maltparser.parser.history.action.GuideUserAction;
014    import org.maltparser.parser.transition.TransitionTable;
015    /**
016     * @author Johan Hall
017     *
018     */
019    public class ArcEager extends TransitionSystem {
020            protected static final int SHIFT = 1;
021            protected static final int REDUCE = 2;
022            protected static final int RIGHTARC = 3;
023            protected static final int LEFTARC = 4;
024            
025            public ArcEager() throws MaltChainedException {
026                    super();
027            }
028            
029            public void apply(GuideUserAction currentAction, ParserConfiguration config) throws MaltChainedException {
030                    NivreConfig nivreConfig = (NivreConfig)config;
031                    Stack<DependencyNode> stack = nivreConfig.getStack();
032                    Stack<DependencyNode> input = nivreConfig.getInput();
033                    currentAction.getAction(actionContainers);
034                    Edge e = null;
035                    switch (transActionContainer.getActionCode()) {
036                    case LEFTARC:
037                            e = nivreConfig.getDependencyStructure().addDependencyEdge(input.peek().getIndex(), stack.peek().getIndex());
038                            addEdgeLabels(e);
039                            stack.pop();
040                            break;
041                    case RIGHTARC:
042                            e = nivreConfig.getDependencyStructure().addDependencyEdge(stack.peek().getIndex(), input.peek().getIndex());
043                            addEdgeLabels(e);
044                            stack.push(input.pop());
045                            break;
046                    case REDUCE:
047                            stack.pop();
048                            break;
049                    default:
050                            stack.push(input.pop()); 
051                            break;
052                    }
053            }
054            
055            public GuideUserAction getDeterministicAction(GuideUserHistory history, ParserConfiguration config) throws MaltChainedException {
056                    NivreConfig nivreConfig = (NivreConfig)config;
057                    if (nivreConfig.getRootHandling() != NivreConfig.NORMAL && nivreConfig.getStack().peek().isRoot()) {
058                            return updateActionContainers(history, ArcEager.SHIFT, null);
059                    }
060                    return null;
061            }
062            
063            protected void addAvailableTransitionToTable(TransitionTable ttable) throws MaltChainedException {
064                    ttable.addTransition(SHIFT, "SH", false, null);
065                    ttable.addTransition(REDUCE, "RE", false, null);
066                    ttable.addTransition(RIGHTARC, "RA", true, null);
067                    ttable.addTransition(LEFTARC, "LA", true, null);
068            }
069            
070            protected void initWithDefaultTransitions(GuideUserHistory history) throws MaltChainedException {
071                    GuideUserAction currentAction = new ComplexDecisionAction((History)history);
072                    
073                    transActionContainer.setAction(SHIFT);
074                    transActionContainer.setAction(REDUCE);
075                    for (int i = 0; i < arcLabelActionContainers.length; i++) {
076                            arcLabelActionContainers[i].setAction(-1);
077                    }
078                    currentAction.addAction(actionContainers);
079            }
080            
081            public String getName() {
082                    return "nivreeager";
083            }
084    
085            public boolean permissible(GuideUserAction currentAction, ParserConfiguration config) throws MaltChainedException {
086                    currentAction.getAction(actionContainers);
087                    int trans = transActionContainer.getActionCode();
088                    DependencyNode stackPeek = ((NivreConfig)config).getStack().peek();
089                    int rootHandling = ((NivreConfig)config).getRootHandling();
090                    if ((trans == LEFTARC || trans == RIGHTARC) && !isActionContainersLabeled()) {
091                            return false;
092                    }
093                    if ((trans == LEFTARC || trans == REDUCE) && stackPeek.isRoot()) { 
094                            return false;
095                    }
096                    if (trans == LEFTARC && stackPeek.hasHead()) { 
097                            return false;
098                    }
099                    if (trans == REDUCE && !stackPeek.hasHead() && rootHandling == NivreConfig.STRICT) {
100                            return false;
101                    }
102                    return true;
103            }
104            
105            public GuideUserAction defaultAction(GuideUserHistory history, ParserConfiguration configuration) throws MaltChainedException {
106                    return updateActionContainers(history, ArcEager.SHIFT, null);
107            }
108    }