/**
  * 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 binaere Plus
 *
 */

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

public
class BinaryMinus extends BinaryExpr {

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

  public
  BinaryMinus(Expr left, Expr right) {
    super(left, right);
  }

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

  // eval wertet den Operanden aus

  public
  Object eval() {

    // beide Operanden auswerten
    Object value1
      = left.eval();

    Object value2
      = right.eval();

    // - fuer int
    if ( value1 instanceof Integer
	 &&
	 value2 instanceof Integer ) {

      return
	new Integer( ((Integer)value1).intValue()
		     -
		     ((Integer)value2).intValue() );
    }

    // - fuer double
    if ( value1 instanceof Double
	 &&
	 value2 instanceof Double ) {

      return
	new Double( ((Double)value1).doubleValue()
		     -
		     ((Double)value2).doubleValue() );
    }

    // nicht erlaubtes Argument
    throw
      new IllegalArgumentException("binary - : illegal operand types");
  }

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

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

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