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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.lexparser;

import java.io.Serializable;

import edu.stanford.nlp.util.Index;
import edu.stanford.nlp.util.StringUtils;

/**
 * Binary rules (ints for parent, left and right children)
 *
 * @author Dan Klein
 * @author Christopher Manning
 */
public class BinaryRule implements Rule, Comparable, Serializable {

  public int parent;
  /**
   * Score should be a log probability
   */
  public float score;
  public int leftChild;
  public int rightChild;

  /** Create a new BinaryRule with the parent and children coded as ints.
   *  Score defaults to Float.NaN.
   *  @param parent The parent int
   *  @param leftChild The left child int
   *  @param rightChild The right child int
   */
  public BinaryRule(int parent, int leftChild, int rightChild) {
    this.parent = parent;
    this.leftChild = leftChild;
    this.rightChild = rightChild;
    this.score = Float.NaN;
  }

  public BinaryRule(int parent, int leftChild, int rightChild, double score) {
    this.parent = parent;
    this.leftChild = leftChild;
    this.rightChild = rightChild;
    this.score = (float) score;
  }

  /**
   * Creates a BinaryRule from String s, assuming it was created using toString().
   *
   * @param s A String in which the binary rule is represented as parent,
   *     left-child, right-child, score, with the items quoted as needed
   * @param index Index used to convert String names to ints
   */
  public BinaryRule(String s, Index index) {
    String[] fields = StringUtils.splitOnCharWithQuoting(s, ' ', '\"', '\\');
    //    System.out.println("fields:\n" + fields[0] + "\n" + fields[2] + "\n" + fields[3] + "\n" + fields[4]);
    this.parent = index.addToIndex(fields[0]);
    this.leftChild = index.addToIndex(fields[2]);
    this.rightChild = index.addToIndex(fields[3]);
    this.score = Float.parseFloat(fields[4]);
  }

  public float score() {
    return score;
  }

  public int parent() {
    return parent;
  }

  private int hashCode = -1;

  @Override
  public int hashCode() {
    if (hashCode < 0) {
      hashCode = (parent << 16) ^ (leftChild << 8) ^ rightChild;
    }
    return hashCode;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o instanceof BinaryRule) {
      BinaryRule br = (BinaryRule) o;
      if (parent == br.parent && leftChild == br.leftChild && rightChild == br.rightChild) {
        return true;
      }
    }
    return false;
  }

  private static final char[] charsToEscape = { '\"' };


  public String toString() {
    return parent + " -> " + leftChild + ' ' + rightChild + ' ' + score;
  }

  public String toString(Index index) {
    return '\"' + StringUtils.escapeString(index.get(parent), charsToEscape, '\\') + "\" -> \"" + StringUtils.escapeString(index.get(leftChild), charsToEscape, '\\') + "\" \"" + StringUtils.escapeString(index.get(rightChild), charsToEscape, '\\') + "\" " + score;
  }

  private transient String cached; // = null;

  public String toStringNoScore(Index index) {
    if (cached == null) {
      cached = '\"' + StringUtils.escapeString(index.get(parent), charsToEscape, '\\') + "\" -> \"" + StringUtils.escapeString(index.get(leftChild), charsToEscape, '\\') + "\" \"" + StringUtils.escapeString(index.get(rightChild), charsToEscape, '\\');
    }
    return cached;
  }

  public int compareTo(BinaryRule br) {
    if (parent < br.parent) {
      return -1;
    }
    if (parent > br.parent) {
      return 1;
    }
    if (leftChild < br.leftChild) {
      return -1;
    }
    if (leftChild > br.leftChild) {
      return 1;
    }
    if (rightChild < br.rightChild) {
      return -1;
    }
    if (rightChild > br.rightChild) {
      return 1;
    }
    return 0;
  }

  private static final long serialVersionUID = 1L;

}