package LBJ2.IR;

import LBJ2.Pass;


/**
  * This class represents an expression involving a unary operator.
  *
  * @author Nick Rizzolo
 **/
public class UnaryExpression extends Expression
{
  /** (¬ø) Representation of the unary operator. */
  public Operator operation;
  /** (¬ø) The expression on which the unary operator operates. */
  public Expression subexpression;


  /**
    * Initializing constructor.  Line and byte offset information is taken
    * from the unary operator's representation.
    *
    * @param op   Representation of the unary operator.
    * @param sub  The expression on which the unary operator operates.
   **/
  public UnaryExpression(Operator op, Expression sub) {
    super(op.line, op.byteOffset);
    operation = op;
    subexpression = sub;
  }


  /**
    * Returns a hash code value for java hash structures.
    *
    * @return A hash code for this object.
   **/
  public int hashCode() {
    return operation.hashCode() + subexpression.hashCode();
  }


  /**
    * Indicates whether some other object is "equal to" this one.
    *
    * @return <code>true</code> iff this object is the same as the argument.
   **/
  public boolean equals(Object o) {
    if (!(o instanceof UnaryExpression)) return false;
    UnaryExpression u = (UnaryExpression) o;
    return operation.equals(u.operation)
           && subexpression.equals(u.subexpression);
  }


  /**
    * Returns an iterator used to successively access the children of this
    * node.
    *
    * @return An iterator used to successively access the children of this
    *         node.
   **/
  public ASTNodeIterator iterator() {
    ASTNodeIterator I = new ASTNodeIterator(2);
    I.children[0] = operation;
    I.children[1] = subexpression;
    return I;
  }


  /**
    * Creates a new object with the same primitive data, and recursively
    * creates new member data objects as well.
    *
    * @return The clone node.
   **/
  public Object clone() {
    return new UnaryExpression((Operator) operation.clone(),
                               (Expression) subexpression.clone());
  }


  /**
    * Ensures that the correct <code>run()</code> method is called for this
    * type of node.
    *
    * @param pass The pass whose <code>run()</code> method should be called.
   **/
  public void runPass(Pass pass) { pass.run(this); }


  /**
    * Writes a string representation of this <code>ASTNode</code> to the
    * specified buffer.  The representation written is parsable by the LBJ2
    * compiler, but not very readable.
    *
    * @param buffer The buffer to write to.
   **/
  public void write(StringBuffer buffer) {
    if (parenthesized) buffer.append("(");
    operation.write(buffer);
    subexpression.write(buffer);
    if (parenthesized) buffer.append(")");
  }
}