/**
  * Copyright (c): Uwe Schmidt, FH Wedel
  *
  * You may study, modify and distribute this source code
  * FOR NON-COMMERCIAL PURPOSES ONLY.
  * This copyright message has to remain unchanged.
  *
  * Note that this document is provided 'as is',
  * WITHOUT WARRANTY of any kind either expressed or implied.
  */

/**
 * eine Klasse fuer das unaere Minus
 *
 */

//--------------------

public
class UnaryMinus extends UnaryExpr {

  //--------------------

  public
  UnaryMinus(Expr operand) {
    super(operand);
  }

  //--------------------

  // eval wertet den Operanden aus
  // und negiert den Wert
  // Operation erlaubt fuer int und double Werte

  public
  Object eval() {

    // operand auswerten

    Object value
      = operand.eval();

    // - fuer int

    if ( value instanceof Integer ) {
      return
	new Integer(- ((Integer)value).intValue());
    }

    // - fuer double

    if ( value instanceof Double ) {
      return
	new Double(- ((Double)value).doubleValue());
    }

    // nicht erlaubtes Argument

    throw
      new IllegalArgumentException("unary - : illegal operand type");
  }

  //--------------------

  public
  String toString() {
    return
      "( -" + operand.toString() + ")";
  }
}

//--------------------