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The Berkeley parser analyzes the grammatical structure of natural language using probabilistic context-free grammars (PCFGs).

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/**
 * 
 */
package edu.berkeley.nlp.discPCFG;

import edu.berkeley.nlp.util.Indexer;
import edu.berkeley.nlp.util.SubIndexer;

/**
 * The Encoding maintains correspondences between the various representions of the data, labels, and features.  The
 * external representations of labels and features are object-based.  The functions getLabelIndex() and
 * getFeatureIndex() can be used to translate those objects to integer representatiosn: numbers between 0 and
 * getNumLabels() or getNumFeatures() (exclusive).  The inverses of this map are the getLabel() and getFeature()
 * functions.
 */
public class Encoding  {
  Indexer featureIndexer;
  SubIndexer labelIndexer;

  public int getNumFeatures() {
    return featureIndexer.size();
  }

  public int getFeatureIndex(F feature) {
    return featureIndexer.indexOf(feature);
  }

  public F getFeature(int featureIndex) {
    return featureIndexer.get(featureIndex);
  }

  /** Number of labels (not total number of substates) */
  public int getNumLabels() {
    return labelIndexer.size();
  }

  /** Total number of substates */
  public int getNumSubLabels() {
    return labelIndexer.totalSize();
  }

  public int getLabelIndex(L label) {
    return labelIndexer.indexOf(label);
  }

  public int getLabelSubindexBegin(int labelIndex) {
    return labelIndexer.subindexBegin(labelIndex);
  }

  public int getLabelSubindexEnd(int labelIndex) {
    return labelIndexer.subindexEnd(labelIndex);
  }

  public L getLabel(int labelIndex) {
    return labelIndexer.get(labelIndex);
  }

  public Encoding(Indexer featureIndexer, SubIndexer labelIndexer) {
    this.featureIndexer = featureIndexer;
    this.labelIndexer = labelIndexer;
  }
}