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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;

/**
 * Unary grammar rules (with ints for parent and child).
 *
 * @author Dan Klein
 * @author Christopher Manning
 */
public class UnaryRule implements Rule, Comparable, Serializable {

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

  /** The score is set to Float.NaN by default.
   *
   *  @param parent Parent state
   *  @param child Child state
   */
  public UnaryRule(int parent, int child) {
    this.parent = parent;
    this.child = child;
    this.score = Float.NaN;
  }

  public UnaryRule(int parent, int child, double score) {
    this.parent = parent;
    this.child = child;
    this.score = (float) score;
  }

  /** Decode a UnaryRule out of a String representation with help from
   *  an Index.
   *
   *  @param s The String representation
   *  @param index The Index used to convert String to int
   */
  public UnaryRule(String s, Index index) {
    String[] fields = StringUtils.splitOnCharWithQuoting(s, ' ', '\"', '\\');
    //    System.out.println("fields:\n" + fields[0] + "\n" + fields[2] + "\n" + fields[3]);
    this.parent = index.indexOf(fields[0]);
    this.child = index.indexOf(fields[2]);
    this.score = Float.parseFloat(fields[3]);
  }

  public float score() {
    return score;
  }

  public int parent() {
    return parent;
  }

  @Override
  public int hashCode() {
    return (parent << 16) ^ child;
  }

  /** A UnaryRule is equal to another UnaryRule with the same parent and child.
   *  The score is not included in the equality computation.
   *
   * @param o Object to be compared with
   * @return Whether the object is equal to this
   */
  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o instanceof UnaryRule) {
      UnaryRule ur = (UnaryRule) o;
      if (parent == ur.parent && child == ur.child) {
        return true;
      }
    }
    return false;
  }

  public int compareTo(UnaryRule ur) {
    if (parent < ur.parent) {
      return -1;
    }
    if (parent > ur.parent) {
      return 1;
    }
    if (child < ur.child) {
      return -1;
    }
    if (child > ur.child) {
      return 1;
    }
    return 0;
  }

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

  @Override
  public String toString() {
    return parent + " -> " + child + ' ' + score;
  }

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

  private static final long serialVersionUID = 1L;

}