/**
  * 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.
  */

abstract
class UnaryExpr extends Expr {

  // der Operanden-Ausdruck

  protected
  Expr operand;

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

  protected
  UnaryExpr(Expr operand) {
    this.operand = operand;
  }

  public Object eval() {
      Object v1 = operand.eval();
      return
        op1(v1);
  }

  public
  String toString() {
    return
      "(" +
      op1ToString() +
      operand.toString() +
      ")";
  }

  // Schablonenmethoden fuer einstellige Operationen

  protected abstract Object op1(Object v1);
  protected abstract String op1ToString();
}