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Stanford CoreNLP provides a set of natural language analysis tools which can take raw English language text input and give the base forms of words, their parts of speech, whether they are names of companies, people, etc., normalize dates, times, and numeric quantities, mark up the structure of sentences in terms of phrases and word dependencies, and indicate which noun phrases refer to the same entities. It provides the foundational building blocks for higher level text understanding applications.

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package edu.stanford.nlp.parser.shiftreduce;

import java.util.List;

import edu.stanford.nlp.ling.CoreLabel;
import edu.stanford.nlp.tagger.maxent.Distsim;

/**
 * Featurizes words based only on their distributional similarity classes.
 * Borrows the Distsim class from the tagger.
 *
 * @author John Bauer
 */
public class DistsimFeatureFactory extends FeatureFactory {
  private final Distsim distsim;

  DistsimFeatureFactory() {
    throw new UnsupportedOperationException("Illegal construction of DistsimFeatureFactory.  It must be created with a path to a cluster file");
  }

  DistsimFeatureFactory(String path) {
    distsim = Distsim.initLexicon(path);
  }

  public void addDistsimFeatures(List features, CoreLabel label, String featureName) {
    if (label == null) {
      return;
    }

    String word = getFeatureFromCoreLabel(label, FeatureComponent.HEADWORD);
    String tag = getFeatureFromCoreLabel(label, FeatureComponent.HEADTAG);

    String cluster = distsim.getMapping(word);

    features.add(featureName + "dis-" + cluster);
    features.add(featureName + "disT-" + cluster + "-" + tag);
  }

  @Override
  public List featurize(State state, List features) {
    CoreLabel s0Label = getStackLabel(state.stack, 0); // current top of stack
    CoreLabel s1Label = getStackLabel(state.stack, 1); // one previous
    CoreLabel q0Label = getQueueLabel(state.sentence, state.tokenPosition, 0); // current location in queue

    addDistsimFeatures(features, s0Label, "S0");
    addDistsimFeatures(features, s1Label, "S1");
    addDistsimFeatures(features, q0Label, "Q0");

    return features;
  }

  private static final long serialVersionUID = -396152777907151063L;
}