preconditionnegation.java

来自「SHOP2 一个人工智能里面关于任务分解和任务规划的系统。JSHOP2是其jav」· Java 代码 · 共 74 行

package JSHOP2;

/** This class represents an iterator over all the possible bindings that can
 *  satisfy a negation logical expression at run time. Note that in this case
 *  there is at most one such binding, and that is the empty binding.
 *
 *  @author Okhtay Ilghami
 *  @author <a href="http://www.cs.umd.edu/~okhtay">http://www.cs.umd.edu/~okhtay</a>
 *  @version 1.0.3
*/
public class PreconditionNegation extends Precondition
{
  /** The logical expression the negation of which this object represents.
  */
  private Precondition p;

  /** The array this object will return as its next binding.
  */
  private Term[] retVal;

  /** To initialize this negation logical expression.
   *
   *  @param pIn
   *          the logical expression the negation of which this object
   *          represents.
   *  @param vars
   *          the number of variables this logical expression has. This is used
   *          to return a binding of the appropriate size.
  */
  public PreconditionNegation(Precondition pIn, int vars)
  {
    //-- A negative logical expression can be satisfied only once, so pretend
    //-- that this negative logical expression is marked ':first'.
    setFirst(true);

    p = pIn;

    //-- A negation never binds any variable to anything. It is merely a check
    //-- if something is true or not. Therefore, only an empty binding should
    //-- be returned by this object.
    retVal = new Term[vars];
    for (int i = 0; i < vars; i++)
      retVal[i] = null;
  }

  /** To bind the negation logical expression to some binding.
  */
  public void bind(Term[] binding)
  {
    p.bind(binding);
  }

  /** To return the next satisfier for this negation logical expression.
  */
  protected Term[] nextBindingHelper()
  {
    //-- If the logical expression the negation of which this object represents
    //-- can be satisfied, return null, otherwise return an empty binding.
    if (p.nextBinding() != null)
      return null;
    else
      return retVal;
  }

  /** To reset this negation logical expression.
  */
  protected void resetHelper()
  {
    //-- Reset the logical expression the negation of which this object
    //-- represents.
    p.reset();
  }
}