content: package aima.core.logic.fol.parsing.ast;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  import aima.core.logic.fol.Connectors;
  import aima.core.logic.fol.parsing.FOLVisitor;
  
  /**
   * @author Ravi Mohan
   * @author Ciaran O'Reilly
   */
  public class NotSentence implements Sentence {
  	private Sentence negated;
  	private List<Sentence> args = new ArrayList<Sentence>();
  	private String stringRep = null;
  	private int hashCode = 0;
  
  	public NotSentence(Sentence negated) {
  		this.negated = negated;
  		args.add(negated);
  	}
  
  	public Sentence getNegated() {
  		return negated;
  	}
  
  	//
  	// START-Sentence
  	public String getSymbolicName() {
  		return Connectors.NOT;
  	}
  
  	public boolean isCompound() {
  		return true;
  	}
  
  	public List<Sentence> getArgs() {
  		return Collections.unmodifiableList(args);
  	}
  
  	public Object accept(FOLVisitor v, Object arg) {
  		return v.visitNotSentence(this, arg);
  	}
  
  	public NotSentence copy() {
  		return new NotSentence(negated.copy());
  	}
  
  	// END-Sentence
  	//
  
  	@Override
  	public boolean equals(Object o) {
  
  		if (this == o) {
  			return true;
  		}
  		if ((o == null) || (this.getClass() != o.getClass())) {
  			return false;
  		}
  		NotSentence ns = (NotSentence) o;
  		return (ns.negated.equals(negated));
  	}
  
  	@Override
  	public int hashCode() {
  		if (0 == hashCode) {
  			hashCode = 17;
  			hashCode = 37 * hashCode + negated.hashCode();
  		}
  		return hashCode;
  	}
  
  	@Override
  	public String toString() {
  		if (null == stringRep) {
  			StringBuilder sb = new StringBuilder();
  			sb.append("NOT(");
  			sb.append(negated.toString());
  			sb.append(")");
  			stringRep = sb.toString();
  		}
  		return stringRep;
  	}
  }
  